Financial modelling and business forecasting

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(1)

Means, standard deviations and correlations

The dataset is: new09.in7

The sample is: 1973(4) - 1990(2)

Means

LBelgium LFrance LGermanyLFrance/BelgiumLFrance/GermanyLBelgium/Germany

3.8105 3.7169 3.9794 -1.9465 0.92657 2.8731

Standard deviations (using T-1)

LBelgium LFrance LGermanyLFrance/BelgiumLFrance/GermanyLBelgium/Germany

0.29047 0.42521 0.17195 0.10754 0.23542 0.13881

Correlation matrix:

LBelgium LFrance LGermanyLFrance/Belgium

LBelgium 1.0000 0.99593 0.99555 0.92029

LFrance 0.99593 1.0000 0.99782 0.91758

LGermany 0.99555 0.99782 1.0000 0.91119

LFrance/Belgium 0.92029 0.91758 0.91119 1.0000

LFrance/Germany 0.97657 0.98038 0.97257 0.94242

LBelgium/Germany 0.94326 0.95181 0.94353 0.82359

LFrance/GermanyLBelgium/Germany

LBelgium 0.97657 0.94326

LFrance 0.98038 0.95181

LGermany 0.97257 0.94353

LFrance/Belgium 0.94242 0.82359

LFrance/Germany 1.0000 0.96585

LBelgium/Germany 0.96585 1.0000

Normality tests and descriptive statistics

The dataset is: new09.in7

The sample is: 1973(5) - 1990(2)

Normality test for DLBelgium

Observations 202

Mean 0.0049006

Std.Devn. 0.0040206

Skewness 0.55869

Excess Kurtosis -0.35971

Minimum -0.0029746

Maximum 0.016097

Asymptotic test: Chi^2(2) = 11.597 [0.0030]**

Normality test: Chi^2(2) = 23.525 [0.0000]**

Normality test for DLFrance

Observations 202

Mean 0.0067183

Std.Devn. 0.0037830

Skewness 0.28292

Excess Kurtosis -0.22797

Minimum -0.0024968

Maximum 0.019186

Asymptotic test: Chi^2(2) = 3.1322 [0.2089]

Normality test: Chi^2(2) = 3.9005 [0.1422]

Normality test for DLGermany

Observations 202

Mean 0.0028933

Std.Devn. 0.0030606

Skewness 0.59041

Excess Kurtosis 0.35519

Minimum -0.0033465

Maximum 0.012716

Asymptotic test: Chi^2(2) = 12.798 [0.0017]**

Normality test: Chi^2(2) = 12.800 [0.0017]**

Normality test for DLFrance/Belgium

Observations 202

Mean 0.0017844

Std.Devn. 0.011918

Skewness 0.48711

Excess Kurtosis 4.8743

Minimum -0.055216

Maximum 0.043456

Asymptotic test: Chi^2(2) = 207.95 [0.0000]**

Normality test: Chi^2(2) = 83.018 [0.0000]**

Normality test for DLFrance/Germany

Observations 202

Mean 0.0037082

Std.Devn. 0.012603

Skewness 1.0110

Excess Kurtosis 3.1420

Minimum -0.038558

Maximum 0.050134

Asymptotic test: Chi^2(2) = 117.50 [0.0000]**

Normality test: Chi^2(2) = 28.248 [0.0000]**

Normality test for DLBelgium/Germany

Observations 202

Mean 0.0019238

Std.Devn. 0.0078273

Skewness 4.2544

Excess Kurtosis 31.142

Minimum -0.018404

Maximum 0.069908

Asymptotic test: Chi^2(2) = 8772.2 [0.0000]**

Normality test: Chi^2(2) = 415.61 [0.0000]**

(2) Unit-root test

Stationary

EQ( 1) Modelling DLFrance by OLS

The dataset is: new09.in7

The estimation sample is: 1973(5) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

Constant -0.0160450 0.007638 -2.10 0.0369 0.0217

Trend -0.000107278 1.858e-005 -5.77 0.0000 0.1435

LFrance_1 0.00908918 0.002558 3.55 0.0005 0.0597

sigma 0.00279924 RSS 0.00155930985

R^2 0.460593 F(2,199) = 84.96 [0.000]**

log-likelihood 902.324 DW 1.08

no. of observations 202 no. of parameters 3

mean(DLFrance) 0.00671834 var(DLFrance) 1.43108e-005

// Batch code for EQ( 1)

module("PcGive");

package("PcGive", "Single-equation");

usedata("new09.in7");

system

{

Y = DLFrance;

Z = Constant, Trend, LFrance_1;

}

estimate("OLS", 1973, 5, 1990, 2);

EQ( 2) Modelling DLFrance by OLS

The dataset is: new09.in7

The estimation sample is: 1973(5) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

Constant 0.0269034 0.001874 14.4 0.0000 0.5076

LFrance_1 -0.00543452 0.0005012 -10.8 0.0000 0.3702

sigma 0.00301714 RSS 0.00182062088

R^2 0.370198 F(1,200) = 117.6 [0.000]**

log-likelihood 886.676 DW 0.911

no. of observations 202 no. of parameters 2

mean(DLFrance) 0.00671834 var(DLFrance) 1.43108e-005

EQ( 3) Modelling DLFrance by OLS

The dataset is: new09.in7

The estimation sample is: 1973(5) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

LFrance_1 0.00171584 8.072e-005 21.3 0.0000 0.6921

sigma 0.00428889 RSS 0.00369731806

log-likelihood 815.124 DW 0.452

no. of observations 202 no. of parameters 1

mean(DLFrance) 0.00671834 var(DLFrance) 1.43108e-005

EQ( 4) Modelling DLBelgium by OLS

The dataset is: new09.in7

The estimation sample is: 1973(5) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

Constant 0.0215108 0.01391 1.55 0.1235 0.0119

Trend -1.75107e-005 2.083e-005 -0.841 0.4015 0.0035

LBelgium_1 -0.00388990 0.004198 -0.927 0.3553 0.0043

sigma 0.00343212 RSS 0.00234411488

R^2 0.282144 F(2,199) = 39.11 [0.000]**

log-likelihood 861.15 DW 1.34

no. of observations 202 no. of parameters 3

mean(DLBelgium) 0.00490063 var(DLBelgium) 1.61655e-005

EQ( 5) Modelling DLBelgium by OLS

The dataset is: new09.in7

The estimation sample is: 1973(5) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

Constant 0.0328908 0.003186 10.3 0.0000 0.3476

LBelgium_1 -0.00734906 0.0008341 -8.81 0.0000 0.2796

sigma 0.00342961 RSS 0.00235244174

R^2 0.279594 F(1,200) = 77.62 [0.000]**

log-likelihood 860.792 DW 1.33

no. of observations 202 no. of parameters 2

mean(DLBelgium) 0.00490063 var(DLBelgium) 1.61655e-005

EQ( 6) Modelling DLBelgium by OLS

The dataset is: new09.in7

The estimation sample is: 1973(5) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

LBelgium_1 0.00123717 7.802e-005 15.9 0.0000 0.5557

sigma 0.00423554 RSS 0.00360589874

log-likelihood 817.653 DW 0.874

no. of observations 202 no. of parameters 1

mean(DLBelgium) 0.00490063 var(DLBelgium) 1.61655e-005

EQ( 7) Modelling DLGermany by OLS

The dataset is: new09.in7

The estimation sample is: 1973(5) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

Constant 0.0218191 0.01885 1.16 0.2484 0.0067

Trend -6.70422e-006 1.501e-005 -0.447 0.6557 0.0010

LGermany_1 -0.00458449 0.005113 -0.897 0.3710 0.0040

sigma 0.00284988 RSS 0.00161623889

R^2 0.145862 F(2,199) = 16.99 [0.000]**

log-likelihood 898.702 DW 1.26

no. of observations 202 no. of parameters 3

mean(DLGermany) 0.00289333 var(DLGermany) 9.36755e-006

EQ( 8) Modelling DLGermany by OLS

The dataset is: new09.in7

The estimation sample is: 1973(5) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

Constant 0.0299740 0.004654 6.44 0.0000 0.1718

LGermany_1 -0.00680706 0.001169 -5.82 0.0000 0.1450

sigma 0.00284417 RSS 0.00161785847

R^2 0.145006 F(1,200) = 33.92 [0.000]**

log-likelihood 898.601 DW 1.26

no. of observations 202 no. of parameters 2

mean(DLGermany) 0.00289333 var(DLGermany) 9.36755e-006

EQ( 9) Modelling DLGermany by OLS

The dataset is: new09.in7

The estimation sample is: 1973(5) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

LGermany_1 0.000713342 5.508e-005 13.0 0.0000 0.4549

sigma 0.00311743 RSS 0.00195338812

log-likelihood 879.567 DW 1.05

no. of observations 202 no. of parameters 1

mean(DLGermany) 0.00289333 var(DLGermany) 9.36755e-006

EQ(10) Modelling DLFrance/Belgium by OLS

The dataset is: new09.in7

The estimation sample is: 1973(5) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

Constant -0.0820533 0.04060 -2.02 0.0446 0.0201

Trend 5.27450e-005 3.517e-005 1.50 0.1353 0.0112

LFrance/Belgium_1 -0.0402793 0.01914 -2.10 0.0366 0.0218

sigma 0.0118449 RSS 0.0279202324

R^2 0.0269562 F(2,199) = 2.756 [0.066]

log-likelihood 610.928 DW 1.23

no. of observations 202 no. of parameters 3

mean(Y) 0.00178439 var(Y) 0.000142048

EQ(11) Modelling DLFrance/Belgium by OLS

The dataset is: new09.in7

The estimation sample is: 1973(5) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

Constant -0.0255781 0.01521 -1.68 0.0943 0.0139

LFrance/Belgium_1 -0.0140523 0.007802 -1.80 0.0732 0.0160

sigma 0.0118819 RSS 0.0282357082

R^2 0.0159616 F(1,200) = 3.244 [0.073]

log-likelihood 609.793 DW 1.25

no. of observations 202 no. of parameters 2

mean(Y) 0.00178439 var(Y) 0.000142048

EQ(12) Modelling DLFrance/Belgium by OLS

The dataset is: new09.in7

The estimation sample is: 1973(5) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

LFrance/Belgium_1 -0.000956051 0.0004306 -2.22 0.0275 0.0239

sigma 0.0119357 RSS 0.0286347099

log-likelihood 608.376 DW 1.25

no. of observations 202 no. of parameters 1

mean(Y) 0.00178439 var(Y) 0.000142048

EQ(17) Modelling DLFrance/Germany by OLS

The dataset is: new09.in7

The estimation sample is: 1973(5) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

Constant 0.0192151 0.009474 2.03 0.0439 0.0203

Trend 7.54858e-005 7.164e-005 1.05 0.2933 0.0055

LFrance/Germany_1 -0.0251260 0.01782 -1.41 0.1600 0.0099

sigma 0.0125617 RSS 0.0314015384

R^2 0.0213727 F(2,199) = 2.173 [0.117]

log-likelihood 599.06 DW 1.24

no. of observations 202 no. of parameters 3

mean(Y) 0.00370822 var(Y) 0.000158848

EQ(18) Modelling DLFrance/Germany by OLS

The dataset is: new09.in7

The estimation sample is: 1973(5) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

Constant 0.00998048 0.003598 2.77 0.0061 0.0370

LFrance/Germany_1 -0.00678005 0.003770 -1.80 0.0736 0.0159

sigma 0.0125652 RSS 0.0315767197

R^2 0.0159132 F(1,200) = 3.234 [0.074]

log-likelihood 598.498 DW 1.25

no. of observations 202 no. of parameters 2

mean(Y) 0.00370822 var(Y) 0.000158848

EQ(19) Modelling DLFrance/Germany by OLS

The dataset is: new09.in7

The estimation sample is: 1973(5) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

LFrance/Germany_1 0.00335708 0.0009417 3.57 0.0005 0.0595

sigma 0.0127727 RSS 0.0327915104

log-likelihood 594.686 DW 1.22

no. of observations 202 no. of parameters 1

mean(Y) 0.00370822 var(Y) 0.000158848

EQ(20) Modelling DLBelgium/Germany by OLS

The dataset is: new09.in7

The estimation sample is: 1973(5) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

Constant 0.0324338 0.03354 0.967 0.3346 0.0047

Trend 1.68881e-005 3.010e-005 0.561 0.5753 0.0016

LBelgium/Germany_1 -0.0112248 0.01269 -0.885 0.3774 0.0039

sigma 0.00785526 RSS 0.0122793188

R^2 0.00780208 F(2,199) = 0.7824 [0.459]

log-likelihood 693.893 DW 1.34

no. of observations 202 no. of parameters 3

mean(Y) 0.00192383 var(Y) 6.12667e-005

EQ(21) Modelling DLBelgium/Germany by OLS

The dataset is: new09.in7

The estimation sample is: 1973(5) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

Constant 0.0147556 0.01147 1.29 0.1998 0.0082

LBelgium/Germany_1 -0.00446743 0.003989 -1.12 0.2641 0.0062

sigma 0.00784179 RSS 0.0122987469

R^2 0.00623224 F(1,200) = 1.254 [0.264]

log-likelihood 693.734 DW 1.34

no. of observations 202 no. of parameters 2

mean(Y) 0.00192383 var(Y) 6.12667e-005

EQ(22) Modelling DLBelgium/Germany by OLS

The dataset is: new09.in7

The estimation sample is: 1973(5) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

LBelgium/Germany_1 0.000657903 0.0001922 3.42 0.0007 0.0551

sigma 0.00785456 RSS 0.0124005016

log-likelihood 692.901 DW 1.34

no. of observations 202 no. of parameters 1

mean(Y) 0.00192383 var(Y) 6.12667e-005

H0 unit root

H1 STATIONARY

ALMOST OF THEM SUGGEST I0

ADF TEST

H0 I(1)

H1 I(2)

EQ(23) Modelling DLBelgium/Germany by OLS

The dataset is: new09.in7

The estimation sample is: 1973(6) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

DLBelgium/Germany_1 0.336949 0.06742 5.00 0.0000 0.1125

LBelgium/Germany_1 -0.0179784 0.01208 -1.49 0.1383 0.0111

Constant 0.0494398 0.03191 1.55 0.1229 0.0120

Trend 3.40206e-005 2.873e-005 1.18 0.2377 0.0071

sigma 0.00743136 RSS 0.0108793353

R^2 0.119947 F(3,197) = 8.95 [0.000]**

log-likelihood 702.125 DW 1.82

no. of observations 201 no. of parameters 4

mean(Y) 0.00194223 var(Y) 6.15032e-005

EQ(24) Modelling DLBelgium/Germany by OLS

The dataset is: new09.in7

The estimation sample is: 1973(6) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

DLBelgium/Germany_1 0.326982 0.06696 4.88 0.0000 0.1075

LBelgium/Germany_1 -0.00439956 0.003809 -1.16 0.2495 0.0067

Constant 0.0139460 0.01096 1.27 0.2047 0.0081

sigma 0.00743891 RSS 0.0109567886

R^2 0.113682 F(2,198) = 12.7 [0.000]**

log-likelihood 701.412 DW 1.82

no. of observations 201 no. of parameters 3

mean(Y) 0.00194223 var(Y) 6.15032e-005

EQ(25) Modelling DLBelgium/Germany by OLS

The dataset is: new09.in7

The estimation sample is: 1973(6) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

DLBelgium/Germany_1 0.329561 0.06703 4.92 0.0000 0.1083

LBelgium/Germany_1 0.000441060 0.0001882 2.34 0.0201 0.0269

sigma 0.00745046 RSS 0.0110463712

log-likelihood 700.594 DW 1.82

no. of observations 201 no. of parameters 2

mean(Y) 0.00194223 var(Y) 6.15032e-005

EQ(26) Modelling DLFrance/Germany by OLS

The dataset is: new09.in7

The estimation sample is: 1973(6) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

DLFrance/Germany_1 0.394828 0.06590 5.99 0.0000 0.1541

Constant 0.0253629 0.008845 2.87 0.0046 0.0401

LFrance/Germany_1 -0.0411394 0.01669 -2.46 0.0146 0.0299

Trend 0.000146035 6.721e-005 2.17 0.0310 0.0234

sigma 0.011599 RSS 0.0265035905

R^2 0.17352 F(3,197) = 13.79 [0.000]**

log-likelihood 612.638 DW 1.94

no. of observations 201 no. of parameters 4

mean(Y) 0.00373002 var(Y) 0.000159542

EQ(27) Modelling DLFrance/Germany by OLS

The dataset is: new09.in7

The estimation sample is: 1973(6) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

DLFrance/Germany_1 0.370646 0.06556 5.65 0.0000 0.1390

Constant 0.00761390 0.003423 2.22 0.0273 0.0244

LFrance/Germany_1 -0.00568251 0.003554 -1.60 0.1115 0.0127

sigma 0.0117074 RSS 0.0271387011

R^2 0.153715 F(2,198) = 17.98 [0.000]**

log-likelihood 610.258 DW 1.92

no. of observations 201 no. of parameters 3

mean(Y) 0.00373002 var(Y) 0.000159542

EQ(28) Modelling DLFrance/Germany by OLS

The dataset is: new09.in7

The estimation sample is: 1973(6) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

DLFrance/Germany_1 0.390919 0.06556 5.96 0.0000 0.1516

LFrance/Germany_1 0.00196840 0.0009030 2.18 0.0304 0.0233

sigma 0.011823 RSS 0.0278166762

log-likelihood 607.779 DW 1.92

no. of observations 201 no. of parameters 2

mean(Y) 0.00373002 var(Y) 0.000159542

EQ(29) Modelling DLBelgium/Germany by OLS

The dataset is: new09.in7

The estimation sample is: 1973(6) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

DLBelgium/Germany_1 0.336949 0.06742 5.00 0.0000 0.1125

Constant 0.0494398 0.03191 1.55 0.1229 0.0120

Trend 3.40206e-005 2.873e-005 1.18 0.2377 0.0071

LBelgium/Germany_1 -0.0179784 0.01208 -1.49 0.1383 0.0111

sigma 0.00743136 RSS 0.0108793353

R^2 0.119947 F(3,197) = 8.95 [0.000]**

log-likelihood 702.125 DW 1.82

no. of observations 201 no. of parameters 4

mean(Y) 0.00194223 var(Y) 6.15032e-005

EQ(30) Modelling DLBelgium/Germany by OLS

The dataset is: new09.in7

The estimation sample is: 1973(6) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

DLBelgium/Germany_1 0.326982 0.06696 4.88 0.0000 0.1075

Constant 0.0139460 0.01096 1.27 0.2047 0.0081

LBelgium/Germany_1 -0.00439956 0.003809 -1.16 0.2495 0.0067

sigma 0.00743891 RSS 0.0109567886

R^2 0.113682 F(2,198) = 12.7 [0.000]**

log-likelihood 701.412 DW 1.82

no. of observations 201 no. of parameters 3

mean(Y) 0.00194223 var(Y) 6.15032e-005

EQ(31) Modelling DLBelgium/Germany by OLS

The dataset is: new09.in7

The estimation sample is: 1973(6) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

DLBelgium/Germany_1 0.329561 0.06703 4.92 0.0000 0.1083

LBelgium/Germany_1 0.000441060 0.0001882 2.34 0.0201 0.0269

sigma 0.00745046 RSS 0.0110463712

log-likelihood 700.594 DW 1.82

no. of observations 201 no. of parameters 2

mean(Y) 0.00194223 var(Y) 6.15032e-005

EQ(32) Modelling DLBelgium by OLS

The dataset is: new09.in7

The estimation sample is: 1973(6) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

DLBelgium_1 0.326990 0.06678 4.90 0.0000 0.1085

Constant 0.0218492 0.01332 1.64 0.1024 0.0135

LBelgium_1 -0.00481865 0.004012 -1.20 0.2312 0.0073

Trend -1.78575e-006 1.997e-005 -0.0894 0.9288 0.0000

sigma 0.00323924 RSS 0.00206705122

R^2 0.366874 F(3,197) = 38.05 [0.000]**

log-likelihood 869.03 DW 2.07

no. of observations 201 no. of parameters 4

mean(DLBelgium) 0.0049045 var(DLBelgium) 1.62429e-005

EQ(33) Modelling DLBelgium by OLS

The dataset is: new09.in7

The estimation sample is: 1973(6) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

DLBelgium_1 0.327704 0.06613 4.96 0.0000 0.1103

Constant 0.0229921 0.003726 6.17 0.0000 0.1613

LBelgium_1 -0.00516766 0.0009288 -5.56 0.0000 0.1352

sigma 0.00323111 RSS 0.00206713512

R^2 0.366848 F(2,198) = 57.36 [0.000]**

log-likelihood 869.025 DW 2.07

no. of observations 201 no. of parameters 3

mean(DLBelgium) 0.0049045 var(DLBelgium) 1.62429e-005

EQ(34) Modelling DLBelgium by OLS

The dataset is: new09.in7

The estimation sample is: 1973(6) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

DLBelgium_1 0.563880 0.05875 9.60 0.0000 0.3165

LBelgium_1 0.000537264 9.763e-005 5.50 0.0000 0.1321

sigma 0.00351932 RSS 0.00246473478

log-likelihood 851.345 DW 2.26

no. of observations 201 no. of parameters 2

mean(DLBelgium) 0.0049045 var(DLBelgium) 1.62429e-005

EQ(35) Modelling DLFrance by OLS

The dataset is: new09.in7

The estimation sample is: 1973(6) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

DLFrance_1 0.465581 0.06391 7.28 0.0000 0.2122

Constant -0.00635720 0.006970 -0.912 0.3628 0.0042

LFrance_1 0.00411569 0.002388 1.72 0.0864 0.0148

Trend -5.22226e-005 1.823e-005 -2.86 0.0046 0.0400

sigma 0.00249668 RSS 0.00122797857

R^2 0.57419 F(3,197) = 88.55 [0.000]**

log-likelihood 921.365 DW 2.13

no. of observations 201 no. of parameters 4

mean(DLFrance) 0.00670529 var(DLFrance) 1.43476e-005

EQ(36) Modelling DLFrance by OLS

The dataset is: new09.in7

The estimation sample is: 1973(6) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

DLFrance_1 0.541023 0.05928 9.13 0.0000 0.2961

Constant 0.0125788 0.002251 5.59 0.0000 0.1363

LFrance_1 -0.00256031 0.0005327 -4.81 0.0000 0.1045

sigma 0.00254171 RSS 0.00127913695

R^2 0.556451 F(2,198) = 124.2 [0.000]**

log-likelihood 917.263 DW 2.2

no. of observations 201 no. of parameters 3

mean(DLFrance) 0.00670529 var(DLFrance) 1.43476e-005

EQ(37) Modelling DLFrance by OLS

The dataset is: new09.in7

The estimation sample is: 1973(6) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

DLFrance_1 0.774790 0.04509 17.2 0.0000 0.5974

LFrance_1 0.000377414 9.312e-005 4.05 0.0001 0.0763

sigma 0.00272799 RSS 0.00148094365

log-likelihood 902.541 DW 2.45

no. of observations 201 no. of parameters 2

mean(DLFrance) 0.00670529 var(DLFrance) 1.43476e-005

EQ(38) Modelling DLGermany by OLS

The dataset is: new09.in7

The estimation sample is: 1973(6) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

DLGermany_1 0.365669 0.06631 5.51 0.0000 0.1337

Constant 0.0197762 0.01776 1.11 0.2667 0.0063

LGermany_1 -0.00453649 0.004816 -0.942 0.3474 0.0045

Trend 9.17538e-007 1.418e-005 0.0647 0.9485 0.0000

sigma 0.00266156 RSS 0.00139552576

R^2 0.254234 F(3,197) = 22.39 [0.000]**

log-likelihood 908.511 DW 2.03

no. of observations 201 no. of parameters 4

mean(DLGermany) 0.00287059 var(DLGermany) 9.30977e-006

EQ(39) Modelling DLGermany by OLS

The dataset is: new09.in7

The estimation sample is: 1973(6) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

DLGermany_1 0.365186 0.06572 5.56 0.0000 0.1349

Constant 0.0186701 0.004802 3.89 0.0001 0.0709

LGermany_1 -0.00423450 0.001187 -3.57 0.0005 0.0604

sigma 0.00265486 RSS 0.00139555543

R^2 0.254218 F(2,198) = 33.75 [0.000]**

log-likelihood 908.509 DW 2.03

no. of observations 201 no. of parameters 3

mean(DLGermany) 0.00287059 var(DLGermany) 9.30977e-006

EQ(40) Modelling DLGermany by OLS

The dataset is: new09.in7

The estimation sample is: 1973(6) - 1990(2)

Coefficient Std.Error t-value t-prob Part.R^2

DLGermany_1 0.468260 0.06223 7.52 0.0000 0.2215

LGermany_1 0.000374458 6.579e-005 5.69 0.0000 0.1400

sigma 0.00274739 RSS 0.00150208012

log-likelihood 901.116 DW 2.11

no. of observations 201 no. of parameters 2

mean(DLGermany) 0.00287059 var(DLGermany) 9.30977e-006

Unit-root tests

The dataset is: new09.in7

The sample is: 1974(5) - 1990(2)

LFrance: ADF tests (T=190, Constant; 5%=-2.88 1%=-3.47)

D-lag t-adf beta Y_1 sigma t-DY_lag t-prob AIC F-prob

12 -1.357 0.99925 0.002062 3.358 0.0010 -12.30

11 -1.542 0.99913 0.002121 0.04993 0.9602 -12.25 0.0010

10 -1.553 0.99912 0.002115 0.7887 0.4314 -12.26 0.0042

9 -1.613 0.99909 0.002112 1.623 0.1063 -12.26 0.0090

8 -1.762 0.99901 0.002122 0.03910 0.9689 -12.26 0.0067

7 -1.782 0.99901 0.002116 -1.004 0.3165 -12.27 0.0142

6 -1.693 0.99906 0.002116 4.666 0.0000 -12.28 0.0183

5 -2.310 0.99866 0.002233 2.328 0.0210 -12.17 0.0000

4 -2.774 0.99840 0.002260 -2.795 0.0057 -12.15 0.0000

3 -2.300 0.99867 0.002301 5.080 0.0000 -12.12 0.0000

2 -3.405* 0.99797 0.002450 2.586 0.0105 -12.00 0.0000

1 -4.317** 0.99751 0.002487 9.193 0.0000 -11.98 0.0000

0 -10.13** 0.99434 0.002988 -11.62 0.0000

LBelgium: ADF tests (T=190, Constant; 5%=-2.88 1%=-3.47)

D-lag t-adf beta Y_1 sigma t-DY_lag t-prob AIC F-prob

12 -1.597 0.99792 0.003028 3.324 0.0011 -11.53

11 -1.894 0.99747 0.003112 -0.2390 0.8114 -11.48 0.0011

10 -1.884 0.99751 0.003104 -0.7801 0.4364 -11.49 0.0046

9 -1.817 0.99761 0.003101 1.347 0.1798 -11.50 0.0097

8 -2.001 0.99739 0.003108 1.148 0.2525 -11.50 0.0103

7 -2.202 0.99715 0.003111 -0.7425 0.4588 -11.50 0.0125

6 -2.115 0.99730 0.003107 1.692 0.0924 -11.51 0.0193

5 -2.457 0.99691 0.003122 2.009 0.0460 -11.50 0.0122

4 -2.943* 0.99635 0.003148 3.500 0.0006 -11.49 0.0051

3 -3.999** 0.99511 0.003242 0.9936 0.3217 -11.44 0.0001

2 -4.581** 0.99471 0.003242 0.9753 0.3307 -11.44 0.0001

1 -5.312** 0.99430 0.003242 4.105 0.0001 -11.45 0.0002

0 -8.407** 0.99199 0.003376 -11.37 0.0000

LGermany: ADF tests (T=190, Constant; 5%=-2.88 1%=-3.47)

D-lag t-adf beta Y_1 sigma t-DY_lag t-prob AIC F-prob

12 -0.9617 0.99863 0.002338 3.426 0.0008 -12.05

11 -1.337 0.99805 0.002408 3.889 0.0001 -11.99 0.0008

10 -1.903 0.99715 0.002502 0.7668 0.4442 -11.92 0.0000

9 -2.039 0.99698 0.002499 1.961 0.0514 -11.93 0.0000

8 -2.395 0.99648 0.002518 1.040 0.2996 -11.92 0.0000

7 -2.650 0.99618 0.002519 1.808 0.0723 -11.92 0.0000

6 -3.180* 0.99554 0.002535 -2.974 0.0033 -11.91 0.0000

5 -2.549 0.99643 0.002588 -0.3619 0.7179 -11.88 0.0000

4 -2.535 0.99654 0.002582 -0.8986 0.3700 -11.89 0.0000

3 -2.411 0.99677 0.002581 1.527 0.1286 -11.89 0.0000

2 -2.785 0.99634 0.002590 0.9681 0.3343 -11.89 0.0000

1 -3.062* 0.99607 0.002590 5.313 0.0000 -11.90 0.0000

0 -4.730** 0.99385 0.002771 -11.77 0.0000

LFrance/Belgium: ADF tests (T=190, Constant; 5%=-2.88 1%=-3.47)

D-lag t-adf beta Y_1 sigma t-DY_lag t-prob AIC F-prob

12 -1.110 0.99116 0.01047 -0.8751 0.3827 -9.048

11 -1.126 0.99105 0.01046 -1.072 0.2852 -9.054 0.3827

10 -1.142 0.99092 0.01047 -2.186 0.0301 -9.058 0.3861

9 -1.188 0.99045 0.01058 1.229 0.2208 -9.042 0.0864

8 -1.165 0.99063 0.01059 2.479 0.0141 -9.044 0.0884

7 -1.143 0.99068 0.01074 0.3712 0.7109 -9.021 0.0152

6 -1.144 0.99069 0.01072 -0.2431 0.8082 -9.031 0.0270

5 -1.149 0.99067 0.01069 -1.023 0.3075 -9.041 0.0454

4 -1.158 0.99060 0.01069 -0.8568 0.3926 -9.046 0.0517

3 -1.161 0.99058 0.01068 -2.119 0.0355 -9.052 0.0636

2 -1.226 0.98997 0.01078 -0.9129 0.3625 -9.039 0.0247

1 -1.289 0.98948 0.01078 5.761 0.0000 -9.045 0.0296

0 -1.090 0.99037 0.01166 -8.892 0.0000

LFrance/Germany: ADF tests (T=190, Constant; 5%=-2.88 1%=-3.47)

D-lag t-adf beta Y_1 sigma t-DY_lag t-prob AIC F-prob

12 -0.6070 0.99789 0.01055 -2.396 0.0176 -9.033

11 -0.5990 0.99789 0.01069 -1.805 0.0728 -9.011 0.0176

10 -0.5818 0.99794 0.01076 -0.3928 0.6949 -9.003 0.0119

9 -0.5804 0.99795 0.01073 1.063 0.2891 -9.013 0.0288

8 -0.5674 0.99800 0.01073 2.019 0.0450 -9.017 0.0376

7 -0.5464 0.99805 0.01083 2.034 0.0434 -9.005 0.0145

6 -0.5394 0.99806 0.01092 0.1321 0.8950 -8.993 0.0057

5 -0.5412 0.99806 0.01089 -0.6065 0.5449 -9.004 0.0107

4 -0.5307 0.99810 0.01087 -0.7124 0.4771 -9.012 0.0165

3 -0.5201 0.99814 0.01086 -0.9540 0.3413 -9.020 0.0231

2 -0.5204 0.99814 0.01085 -0.5035 0.6152 -9.026 0.0274

1 -0.5291 0.99812 0.01083 5.395 0.0000 -9.035 0.0390

0 -0.5403 0.99794 0.01161 -8.901 0.0000

LBelgium/Germany: ADF tests (T=190, Constant; 5%=-2.88 1%=-3.47)

D-lag t-adf beta Y_1 sigma t-DY_lag t-prob AIC F-prob

12 -0.6166 0.99782 0.006538 0.5495 0.5834 -9.990

11 -0.6083 0.99785 0.006525 -1.173 0.2423 -9.998 0.5834

10 -0.6252 0.99779 0.006532 -1.808 0.0722 -10.00 0.4350

9 -0.6861 0.99756 0.006573 0.9361 0.3505 -9.993 0.1806

8 -0.6261 0.99778 0.006571 0.6478 0.5180 -9.999 0.2177

7 -0.5868 0.99793 0.006560 1.005 0.3160 -10.01 0.2881

6 -0.5306 0.99813 0.006560 -0.2897 0.7724 -10.01 0.3028

5 -0.5494 0.99807 0.006544 1.481 0.1402 -10.02 0.3982

4 -0.4962 0.99825 0.006565 1.109 0.2690 -10.02 0.3054

3 -0.4448 0.99843 0.006569 1.607 0.1097 -10.02 0.2985

2 -0.3763 0.99867 0.006597 -1.197 0.2328 -10.02 0.2126

1 -0.4202 0.99852 0.006605 4.826 0.0000 -10.02 0.2005

0 -0.2665 0.99900 0.006985 -9.917 0.0003

(3) 黄色部分是重要的数据

SYS( 1) Estimating the system by OLS

The dataset is: new09.in7

The estimation sample is: 1974(4) - 1990(2)

URF equation for: LFrance/Belgium

Coefficient Std.Error t-value t-prob

LFrance/Belgium_1 1.27793 0.07985 16.0 0.0000

LFrance/Belgium_2 -0.309790 0.1287 -2.41 0.0172

LFrance/Belgium_3 -0.135067 0.1286 -1.05 0.2954

LFrance/Belgium_4 0.0602494 0.1277 0.472 0.6377

LFrance/Belgium_5 -0.0144114 0.1285 -0.112 0.9109

LFrance/Belgium_6 -0.00309561 0.1268 -0.0244 0.9806

LFrance/Belgium_7 0.0294940 0.1275 0.231 0.8174

LFrance/Belgium_8 0.162431 0.1272 1.28 0.2037

LFrance/Belgium_9 -0.0270322 0.1271 -0.213 0.8319

LFrance/Belgium_10 -0.267770 0.1229 -2.18 0.0309

LFrance/Belgium_11 0.111255 0.1227 0.906 0.3661

LFrance/Belgium_12 -0.00155779 0.07546 -0.0206 0.9836

LFrance_1 0.385940 0.4200 0.919 0.3596

LFrance_2 -1.31872 0.7486 -1.76 0.0801

LFrance_3 1.97146 0.7607 2.59 0.0105

LFrance_4 -1.04391 0.7477 -1.40 0.1647

LFrance_5 0.324587 0.7649 0.424 0.6719

LFrance_6 -0.567520 0.7572 -0.750 0.4547

LFrance_7 0.460296 0.7576 0.608 0.5444

LFrance_8 -0.100251 0.7546 -0.133 0.8945

LFrance_9 -0.223160 0.7339 -0.304 0.7615

LFrance_10 0.760773 0.7369 1.03 0.3035

LFrance_11 -1.23509 0.7159 -1.73 0.0865

LFrance_12 0.597129 0.4041 1.48 0.1416

LBelgium_1 -0.0722244 0.2914 -0.248 0.8046

LBelgium_2 0.337063 0.4337 0.777 0.4382

LBelgium_3 -0.410626 0.4445 -0.924 0.3570

LBelgium_4 -0.450874 0.4508 -1.00 0.3188

LBelgium_5 0.432919 0.4426 0.978 0.3295

LBelgium_6 -0.191279 0.4382 -0.437 0.6631

LBelgium_7 0.115131 0.4390 0.262 0.7935

LBelgium_8 -0.250199 0.4402 -0.568 0.5706

LBelgium_9 0.637659 0.4348 1.47 0.1445

LBelgium_10 -0.503691 0.4372 -1.15 0.2511

LBelgium_11 0.479278 0.4390 1.09 0.2766

LBelgium_12 -0.111923 0.2770 -0.404 0.6867

Constant -0.307948 0.1164 -2.65 0.0090

sigma = 0.0101403 RSS = 0.01583507807

URF equation for: LFrance

Coefficient Std.Error t-value t-prob

LFrance/Belgium_1 0.0104870 0.01579 0.664 0.5075

LFrance/Belgium_2 -0.0111617 0.02544 -0.439 0.6614

LFrance/Belgium_3 -0.0237979 0.02544 -0.936 0.3509

LFrance/Belgium_4 0.0589219 0.02525 2.33 0.0209

LFrance/Belgium_5 -0.00695515 0.02541 -0.274 0.7847

LFrance/Belgium_6 -0.0373424 0.02508 -1.49 0.1385

LFrance/Belgium_7 0.0230060 0.02521 0.912 0.3630

LFrance/Belgium_8 -0.0271489 0.02516 -1.08 0.2822

LFrance/Belgium_9 0.0329476 0.02514 1.31 0.1919

LFrance/Belgium_10 -0.0419706 0.02430 -1.73 0.0862

LFrance/Belgium_11 0.0288738 0.02427 1.19 0.2360

LFrance/Belgium_12 -0.00523507 0.01492 -0.351 0.7262

LFrance_1 1.47084 0.08304 17.7 0.0000

LFrance_2 -0.493216 0.1480 -3.33 0.0011

LFrance_3 0.361839 0.1504 2.41 0.0173

LFrance_4 -0.638682 0.1478 -4.32 0.0000

LFrance_5 0.316810 0.1512 2.09 0.0378

LFrance_6 0.290642 0.1497 1.94 0.0540

LFrance_7 -0.320522 0.1498 -2.14 0.0339

LFrance_8 -0.0522679 0.1492 -0.350 0.7266

LFrance_9 0.0848384 0.1451 0.585 0.5596

LFrance_10 0.150978 0.1457 1.04 0.3017

LFrance_11 -0.118942 0.1415 -0.840 0.4020

LFrance_12 -0.0425372 0.07991 -0.532 0.5953

LBelgium_1 -0.103993 0.05762 -1.80 0.0730

LBelgium_2 0.205379 0.08574 2.40 0.0178

LBelgium_3 -0.254146 0.08788 -2.89 0.0044

LBelgium_4 0.0752933 0.08913 0.845 0.3995

LBelgium_5 0.0359132 0.08750 0.410 0.6821

LBelgium_6 0.110359 0.08664 1.27 0.2047

LBelgium_7 -0.131423 0.08680 -1.51 0.1320

LBelgium_8 0.0330297 0.08703 0.380 0.7048

LBelgium_9 0.0910438 0.08597 1.06 0.2912

LBelgium_10 -0.224310 0.08645 -2.59 0.0104

LBelgium_11 0.124484 0.08679 1.43 0.1535

LBelgium_12 0.0203587 0.05477 0.372 0.7106

Constant 0.0354463 0.02301 1.54 0.1255

sigma = 0.00200488 RSS = 0.0006190098657

URF equation for: LBelgium

Coefficient Std.Error t-value t-prob

LFrance/Belgium_1 0.00357489 0.02257 0.158 0.8743

LFrance/Belgium_2 -0.0126261 0.03636 -0.347 0.7289

LFrance/Belgium_3 -0.00383292 0.03636 -0.105 0.9162

LFrance/Belgium_4 0.0264039 0.03609 0.732 0.4655

LFrance/Belgium_5 -0.0208393 0.03632 -0.574 0.5670

LFrance/Belgium_6 -0.00161438 0.03585 -0.0450 0.9641

LFrance/Belgium_7 -0.0247817 0.03604 -0.688 0.4927

LFrance/Belgium_8 0.0423463 0.03596 1.18 0.2408

LFrance/Belgium_9 -0.00238368 0.03593 -0.0663 0.9472

LFrance/Belgium_10 -0.0369844 0.03474 -1.06 0.2887

LFrance/Belgium_11 0.0293605 0.03469 0.846 0.3986

LFrance/Belgium_12 -0.0180046 0.02133 -0.844 0.3998

LFrance_1 -0.0995052 0.1187 -0.838 0.4032

LFrance_2 0.165785 0.2116 0.784 0.4345

LFrance_3 0.101434 0.2150 0.472 0.6377

LFrance_4 -0.177123 0.2113 -0.838 0.4032

LFrance_5 0.0245123 0.2162 0.113 0.9099

LFrance_6 0.340829 0.2140 1.59 0.1133

LFrance_7 -0.374297 0.2141 -1.75 0.0824

LFrance_8 -0.0700255 0.2133 -0.328 0.7431

LFrance_9 0.177214 0.2074 0.854 0.3942

LFrance_10 0.180473 0.2082 0.867 0.3875

LFrance_11 -0.394862 0.2023 -1.95 0.0528

LFrance_12 0.173936 0.1142 1.52 0.1298

LBelgium_1 1.06640 0.08235 12.9 0.0000

LBelgium_2 -0.160496 0.1226 -1.31 0.1923

LBelgium_3 -0.178947 0.1256 -1.42 0.1563

LBelgium_4 0.305609 0.1274 2.40 0.0176

LBelgium_5 -0.0198356 0.1251 -0.159 0.8742

LBelgium_6 -0.126473 0.1238 -1.02 0.3087

LBelgium_7 -0.0291057 0.1241 -0.235 0.8148

LBelgium_8 0.151122 0.1244 1.21 0.2263

LBelgium_9 -0.0326786 0.1229 -0.266 0.7906

LBelgium_10 -0.0869635 0.1236 -0.704 0.4826

LBelgium_11 0.0450370 0.1241 0.363 0.7171

LBelgium_12 -0.00605258 0.07829 -0.0773 0.9385

Constant 0.0622459 0.03289 1.89 0.0603

sigma = 0.00286568 RSS = 0.001264666523

log-likelihood 2436.99964 -T/2log|Omega| 3250.05141

|Omega| 1.6600113e-015 log|Y'Y/T| -6.84461615

R^2(LR) 1 R^2(LM) 0.990616

no. of observations 191 no. of parameters 111

F-test on regressors except unrestricted: F(111,456) = 35967.7 [0.0000] **

F-tests on retained regressors, F(3,152) =

LFrance/Belgium_1 84.5353 [0.000]**LFrance/Belgium_2 1.98731 [0.118]

LFrance/Belgium_3 0.620620 [0.603] LFrance/Belgium_4 1.84291 [0.142]

LFrance/Belgium_5 0.119660 [0.948] LFrance/Belgium_6 0.767952 [0.514]

LFrance/Belgium_7 0.572443 [0.634] LFrance/Belgium_8 1.77795 [0.154]

LFrance/Belgium_9 0.649431 [0.584] LFrance/Belgium_10 2.61722 [0.053]

LFrance/Belgium_11 0.826255 [0.481] LFrance/Belgium_12 0.242228 [0.867]

LFrance_1 112.831 [0.000]** LFrance_2 5.30298 [0.002]**

LFrance_3 3.91118 [0.010]* LFrance_4 6.60333 [0.000]**

LFrance_5 1.52990 [0.209] LFrance_6 1.87779 [0.136]

LFrance_7 2.16555 [0.094] LFrance_8 0.0662745 [0.978]

LFrance_9 0.317530 [0.813] LFrance_10 0.823492 [0.483]

LFrance_11 2.34789 [0.075] LFrance_12 1.90022 [0.132]

LBelgium_1 64.1130 [0.000]** LBelgium_2 3.25593 [0.023]*

LBelgium_3 3.14657 [0.027]* LBelgium_4 2.19467 [0.091]

LBelgium_5 0.372815 [0.773] LBelgium_6 1.27165 [0.286]

LBelgium_7 0.801519 [0.495] LBelgium_8 0.578631 [0.630]

LBelgium_9 1.09842 [0.352] LBelgium_10 2.56105 [0.057]

LBelgium_11 1.01961 [0.386] LBelgium_12 0.117583 [0.950]

Constant 3.88549 [0.010]*

correlation of URF residuals (standard deviations on diagonal)

LFrance/Belgium LFrance LBelgium

LFrance/Belgium 0.010140 0.051944 -0.040747

LFrance 0.051944 0.0020049 0.24802

LBelgium -0.040747 0.24802 0.0028657

correlation between actual and fitted

LFrance/Belgium LFrance LBelgium

0.99549 0.99999 0.99995

I(1) cointegration analysis, 1974(4) - 1990(2)

eigenvalue loglik for rank

2409.911 0

0.15264 2425.728 1

0.081940 2433.893 2

0.032007 2437.000 3

H0:rank<= Trace test [ Prob]

0 54.177 [0.000] **

1 22.542 [0.022] *

2 6.2133 [0.181]

Asymptotic p-values based on: Restricted constant

Restricted variables:

[0] = Constant

Number of lags used in the analysis: 12

beta (scaled on diagonal; cointegrating vectors in columns)

LFrance/Belgium 1.0000 0.80740 -5.6671

LFrance -1.2433 1.0000 1.7194

LBelgium 1.7382 -1.8156 1.0000

Constant -0.18262 4.8069 -22.299

alpha

LFrance/Belgium -0.064213 -0.067818 -0.00028364

LFrance -0.0069044 0.0027978 -0.00092994

LBelgium -0.028709 0.012456 0.00012874

long-run matrix, rank 3

LFrance/Belgium LFrance LBelgium Constant

LFrance/Belgium -0.11736 0.011531 0.011234 -0.30795

LFrance 0.00062463 0.0097832 -0.018011 0.035446

LBelgium -0.019382 0.048371 -0.072388 0.062246

// Batch code for SYS( 1)

module("PcGive");

package("PcGive", "Multiple-equation");

usedata("new09.in7");

system

{

Y = "LFrance/Belgium", LFrance, LBelgium;

Z = Constant, "LFrance/Belgium_1", "LFrance/Belgium_2",

"LFrance/Belgium_3", "LFrance/Belgium_4", "LFrance/Belgium_5",

"LFrance/Belgium_6", "LFrance/Belgium_7", "LFrance/Belgium_8",

"LFrance/Belgium_9", "LFrance/Belgium_10", "LFrance/Belgium_11",

"LFrance/Belgium_12", LFrance_1, LFrance_2, LFrance_3,

LFrance_4, LFrance_5, LFrance_6, LFrance_7, LFrance_8,

LFrance_9, LFrance_10, LFrance_11, LFrance_12, LBelgium_1,

LBelgium_2, LBelgium_3, LBelgium_4, LBelgium_5, LBelgium_6,

LBelgium_7, LBelgium_8, LBelgium_9, LBelgium_10, LBelgium_11,

LBelgium_12;

}

estimate("OLS", 1974, 4, 1990, 2);

dynamics();

SYS( 2) Cointegrated VAR

The dataset is: new09.in7

The estimation sample is: 1974(4) - 1990(2)

Cointegrated VAR (12) in:

[0] = LFrance/Belgium

[1] = LFrance

[2] = LBelgium

Restricted variables:

[0] = Constant

Number of lags used in the analysis: 12

beta

LFrance/Belgium 1.0000

LFrance -1.2433

LBelgium 1.7382

Constant -0.18262

alpha

LFrance/Belgium -0.064213

LFrance -0.0069044

LBelgium -0.028709

Standard errors of alpha

LFrance/Belgium 0.023864

LFrance 0.0046458

LBelgium 0.0066255

Restricted long-run matrix, rank 1

LFrance/Belgium LFrance LBelgium Constant

LFrance/Belgium -0.064213 0.079837 -0.11162 0.011726

LFrance -0.0069044 0.0085843 -0.012001 0.0012609

LBelgium -0.028709 0.035694 -0.049902 0.0052427

Standard errors of long-run matrix

LFrance/Belgium 0.023864 0.029670 0.041480 0.0043579

LFrance 0.0046458 0.0057762 0.0080753 0.00084840

LBelgium 0.0066255 0.0082376 0.011517 0.0012099

Reduced form beta

LFrance/Belgium -1.0000

LFrance 1.2433

LBelgium -1.7382

Constant 0.18262

Standard errors of reduced form beta

LFrance/Belgium 0.00000

LFrance 0.28616

LBelgium 0.45912

Constant 0.72170

Moving-average impact matrix

0.96145 4.6128 -3.2599

1.7958 37.208 -12.965

0.73138 23.960 -7.3983

log-likelihood 2425.72842 -T/2log|Omega| 3238.7802

no. of observations 191 no. of parameters 105

rank of long-run matrix 1 no. long-run restrictions 0

beta is not identified

No restrictions imposed

LFrance/Belgium: Portmanteau(12): 1.48753

LFrance : Portmanteau(12): 8.94026

LBelgium : Portmanteau(12): 8.36552

LFrance/Belgium: Normality test: Chi^2(2) = 38.144 [0.0000]**

LFrance : Normality test: Chi^2(2) = 22.000 [0.0000]**

LBelgium : Normality test: Chi^2(2) = 2.9930 [0.2239]

LFrance/Belgium: ARCH 1-7 test: F(7,142) = 3.9842 [0.0005]**

LFrance : ARCH 1-7 test: F(7,142) = 0.28833 [0.9576]

LBelgium : ARCH 1-7 test: F(7,142) = 0.62275 [0.7365]

LFrance/Belgium: Hetero test: F(72,81) = 0.91774 [0.6438]

LFrance : Hetero test: F(72,81) = 0.50705 [0.9982]

LBelgium : Hetero test: F(72,81) = 0.51161 [0.9979]

Vector Portmanteau(12): 45.4787

Vector Normality test: Chi^2(6) = 61.569 [0.0000]**

Vector Hetero test: F(432,463)= 0.81429 [0.9848]

SYS( 3) Estimating the system by OLS

The dataset is: new09.in7

The estimation sample is: 1974(4) - 1990(2)

URF equation for: LFrance/Germany

Coefficient Std.Error t-value t-prob

LFrance/Germany_1 1.18243 0.08104 14.6 0.0000

LFrance/Germany_2 -0.254381 0.1257 -2.02 0.0447

LFrance/Germany_3 -0.0111361 0.1263 -0.0882 0.9299

LFrance/Germany_4 0.0268588 0.1254 0.214 0.8307

LFrance/Germany_5 -0.0811245 0.1244 -0.652 0.5153

LFrance/Germany_6 0.0385568 0.1183 0.326 0.7450

LFrance/Germany_7 0.138214 0.1182 1.17 0.2442

LFrance/Germany_8 -0.0552427 0.1194 -0.463 0.6442

LFrance/Germany_9 0.0907171 0.1157 0.784 0.4344

LFrance/Germany_10 -0.0938167 0.1118 -0.839 0.4028

LFrance/Germany_11 -0.105044 0.1098 -0.957 0.3401

LFrance/Germany_12 0.00748530 0.07084 0.106 0.9160

LFrance_1 0.568700 0.3908 1.46 0.1476

LFrance_2 -1.66185 0.6607 -2.52 0.0129

LFrance_3 2.12237 0.6768 3.14 0.0021

LFrance_4 -1.31341 0.6667 -1.97 0.0506

LFrance_5 0.906003 0.6936 1.31 0.1935

LFrance_6 -1.40503 0.6899 -2.04 0.0434

LFrance_7 1.08005 0.6955 1.55 0.1225

LFrance_8 -0.128726 0.6988 -0.184 0.8541

LFrance_9 -0.665868 0.6794 -0.980 0.3286

LFrance_10 0.497608 0.6871 0.724 0.4701

LFrance_11 -0.330165 0.6828 -0.484 0.6294

LFrance_12 0.384502 0.3981 0.966 0.3356

LGermany_1 -0.399822 0.3462 -1.15 0.2500

LGermany_2 0.428888 0.5277 0.813 0.4176

LGermany_3 -0.113032 0.5192 -0.218 0.8279

LGermany_4 -0.306531 0.5163 -0.594 0.5536

LGermany_5 0.349434 0.5177 0.675 0.5007

LGermany_6 0.475014 0.5024 0.945 0.3459

LGermany_7 -1.39212 0.5044 -2.76 0.0065

LGermany_8 0.817985 0.5289 1.55 0.1240

LGermany_9 0.545546 0.5297 1.03 0.3046

LGermany_10 -0.227258 0.5266 -0.432 0.6666

LGermany_11 0.284420 0.5199 0.547 0.5851

LGermany_12 -0.450999 0.3254 -1.39 0.1677

Constant -0.131695 0.2478 -0.531 0.5959

sigma = 0.00994372 RSS = 0.01522714336

URF equation for: LFrance

Coefficient Std.Error t-value t-prob

LFrance/Germany_1 0.00237054 0.01727 0.137 0.8910

LFrance/Germany_2 -0.0222292 0.02678 -0.830 0.4079

LFrance/Germany_3 0.0109498 0.02691 0.407 0.6847

LFrance/Germany_4 0.0263148 0.02672 0.985 0.3263

LFrance/Germany_5 0.0127706 0.02651 0.482 0.6306

LFrance/Germany_6 -0.0559919 0.02521 -2.22 0.0278

LFrance/Germany_7 0.0377117 0.02519 1.50 0.1365

LFrance/Germany_8 -0.0132246 0.02544 -0.520 0.6039

LFrance/Germany_9 0.0120699 0.02466 0.489 0.6252

LFrance/Germany_10 -0.0146932 0.02383 -0.617 0.5384

LFrance/Germany_11 -0.00135161 0.02339 -0.0578 0.9540

LFrance/Germany_12 0.00345209 0.01509 0.229 0.8194

LFrance_1 1.39022 0.08326 16.7 0.0000

LFrance_2 -0.322240 0.1408 -2.29 0.0234

LFrance_3 0.167007 0.1442 1.16 0.2486

LFrance_4 -0.556010 0.1421 -3.91 0.0001

LFrance_5 0.372277 0.1478 2.52 0.0128

LFrance_6 0.308417 0.1470 2.10 0.0375

LFrance_7 -0.399356 0.1482 -2.69 0.0078

LFrance_8 -0.0658622 0.1489 -0.442 0.6589

LFrance_9 0.193218 0.1448 1.33 0.1840

LFrance_10 -0.0535239 0.1464 -0.366 0.7152

LFrance_11 -0.0500518 0.1455 -0.344 0.7313

LFrance_12 0.0131828 0.08482 0.155 0.8767

LGermany_1 0.0410234 0.07377 0.556 0.5790

LGermany_2 -0.00344278 0.1124 -0.0306 0.9756

LGermany_3 0.0141478 0.1106 0.128 0.8984

LGermany_4 0.0697912 0.1100 0.634 0.5268

LGermany_5 -0.137718 0.1103 -1.25 0.2138

LGermany_6 0.0525577 0.1071 0.491 0.6242

LGermany_7 -0.0388818 0.1075 -0.362 0.7180

LGermany_8 0.00803967 0.1127 0.0713 0.9432

LGermany_9 -0.0590020 0.1129 -0.523 0.6019

LGermany_10 0.0424012 0.1122 0.378 0.7060

LGermany_11 -0.0357749 0.1108 -0.323 0.7472

LGermany_12 0.0536652 0.06932 0.774 0.4401

Constant -0.0141731 0.05281 -0.268 0.7888

sigma = 0.00211877 RSS = 0.0006913324248

URF equation for: LGermany

Coefficient Std.Error t-value t-prob

LFrance/Germany_1 -0.00995883 0.01876 -0.531 0.5962

LFrance/Germany_2 0.00806314 0.02909 0.277 0.7820

LFrance/Germany_3 0.0364057 0.02923 1.25 0.2149

LFrance/Germany_4 -0.0432459 0.02903 -1.49 0.1383

LFrance/Germany_5 0.00823761 0.02879 0.286 0.7752

LFrance/Germany_6 -0.00739354 0.02738 -0.270 0.7875

LFrance/Germany_7 -0.000402614 0.02737 -0.0147 0.9883

LFrance/Germany_8 0.00640793 0.02763 0.232 0.8169

LFrance/Germany_9 -0.0113554 0.02679 -0.424 0.6722

LFrance/Germany_10 0.00921922 0.02588 0.356 0.7222

LFrance/Germany_11 0.00209335 0.02541 0.0824 0.9344

LFrance/Germany_12 -0.00116559 0.01640 -0.0711 0.9434

LFrance_1 0.116560 0.09044 1.29 0.1994

LFrance_2 -0.0817372 0.1529 -0.535 0.5937

LFrance_3 0.0121145 0.1566 0.0773 0.9385

LFrance_4 0.0130135 0.1543 0.0843 0.9329

LFrance_5 -0.117251 0.1605 -0.730 0.4663

LFrance_6 0.157006 0.1597 0.983 0.3270

LFrance_7 -0.109813 0.1610 -0.682 0.4961

LFrance_8 0.0848636 0.1617 0.525 0.6006

LFrance_9 0.267655 0.1573 1.70 0.0908

LFrance_10 -0.349672 0.1590 -2.20 0.0294

LFrance_11 0.0257251 0.1580 0.163 0.8709

LFrance_12 0.0127173 0.09213 0.138 0.8904

LGermany_1 1.16865 0.08013 14.6 0.0000

LGermany_2 -0.244820 0.1221 -2.00 0.0468

LGermany_3 0.118195 0.1202 0.984 0.3269

LGermany_4 -0.108472 0.1195 -0.908 0.3655

LGermany_5 0.0930923 0.1198 0.777 0.4384

LGermany_6 -0.404054 0.1163 -3.47 0.0007

LGermany_7 0.393746 0.1167 3.37 0.0009

LGermany_8 -0.144701 0.1224 -1.18 0.2390

LGermany_9 0.0697007 0.1226 0.569 0.5705

LGermany_10 -0.00537249 0.1219 -0.0441 0.9649

LGermany_11 0.211525 0.1203 1.76 0.0807

LGermany_12 -0.219975 0.07530 -2.92 0.0040

Constant 0.174402 0.05736 3.04 0.0028

sigma = 0.00230147 RSS = 0.0008156992738

log-likelihood 2474.65444 -T/2log|Omega| 3287.70622

|Omega| 1.11910951e-015 log|Y'Y/T| -6.29263643

R^2(LR) 1 R^2(LM) 0.986345

no. of observations 191 no. of parameters 111

F-test on regressors except unrestricted: F(111,456) = 49332.7 [0.0000] **

F-tests on retained regressors, F(3,152) =

LFrance/Germany_1 72.3906 [0.000]**LFrance/Germany_2 1.56110 [0.201]

LFrance/Germany_3 0.530140 [0.662] LFrance/Germany_4 1.39341 [0.247]

LFrance/Germany_5 0.271015 [0.846] LFrance/Germany_6 1.80232 [0.149]

LFrance/Germany_7 1.10053 [0.351] LFrance/Germany_8 0.190291 [0.903]

LFrance/Germany_9 0.369824 [0.775] LFrance/Germany_10 0.419550 [0.739]

LFrance/Germany_11 0.312637 [0.816] LFrance/Germany_12 0.0250941 [0.995]

LFrance_1 95.1567 [0.000]** LFrance_2 3.29445 [0.022]*

LFrance_3 3.43553 [0.019]* LFrance_4 6.12358 [0.001]**

LFrance_5 3.07888 [0.029]* LFrance_6 3.47117 [0.018]*

LFrance_7 3.72339 [0.013]* LFrance_8 0.215050 [0.886]

LFrance_9 1.79252 [0.151] LFrance_10 1.88604 [0.134]

LFrance_11 0.127775 [0.944] LFrance_12 0.307600 [0.820]

LGermany_1 75.0178 [0.000]** LGermany_2 1.70258 [0.169]

LGermany_3 0.353433 [0.787] LGermany_4 0.668355 [0.573]

LGermany_5 1.15449 [0.329] LGermany_6 5.03881 [0.002]**

LGermany_7 7.14852 [0.000]** LGermany_8 1.38611 [0.249]

LGermany_9 0.651169 [0.583] LGermany_10 0.133081 [0.940]

LGermany_11 1.30487 [0.275] LGermany_12 4.20461 [0.007]**

Constant 3.57993 [0.015]*

correlation of URF residuals (standard deviations on diagonal)

LFrance/Germany LFrance LGermany

LFrance/Germany 0.0099437 0.15995 0.098497

LFrance 0.15995 0.0021188 0.25420

LGermany 0.098497 0.25420 0.0023015

correlation between actual and fitted

LFrance/Germany LFrance LGermany

0.99918 0.99999 0.99991

I(1) cointegration analysis, 1974(4) - 1990(2)

eigenvalue loglik for rank

2451.615 0

0.15287 2467.458 1

0.056413 2473.003 2

0.017142 2474.654 3

H0:rank<= Trace test [ Prob]

0 46.080 [0.002] **

1 14.393 [0.269]

2 3.3025 [0.536]

Asymptotic p-values based on: Restricted constant

Restricted variables:

[0] = Constant

Number of lags used in the analysis: 12

beta (scaled on diagonal; cointegrating vectors in columns)

LFrance/Germany 1.0000 -0.33556 0.052729

LFrance 0.044039 1.0000 -0.31341

LGermany -1.3365 -2.0026 1.0000

Constant 4.1392 4.5402 -2.9665

alpha

LFrance/Germany -0.097026 0.057534 -0.0029306

LFrance -0.0030697 -0.0046797 -0.0066679

LGermany 0.0070976 0.029879 -0.0031577

long-run matrix, rank 3

LFrance/Germany LFrance LGermany Constant

LFrance/Germany -0.11649 0.054180 0.011527 -0.13170

LFrance -0.0018510 -0.0027252 0.0068069 -0.014173

LGermany -0.0030948 0.031181 -0.072480 0.17440

SYS( 4) Cointegrated VAR

The dataset is: new09.in7

The estimation sample is: 1974(4) - 1990(2)

Cointegrated VAR (12) in:

[0] = LFrance/Germany

[1] = LFrance

[2] = LGermany

Restricted variables:

[0] = Constant

Number of lags used in the analysis: 12

beta

LFrance/Germany 1.0000

LFrance 0.044039

LGermany -1.3365

Constant 4.1392

alpha

LFrance/Germany -0.097026

LFrance -0.0030697

LGermany 0.0070976

Standard errors of alpha

LFrance/Germany 0.019970

LFrance 0.0042744

LGermany 0.0047086

Restricted long-run matrix, rank 1

LFrance/Germany LFrance LGermany Constant

LFrance/Germany -0.097026 -0.0042729 0.12968 -0.40161

LFrance -0.0030697 -0.00013519 0.0041029 -0.012706

LGermany 0.0070976 0.00031257 -0.0094863 0.029379

Standard errors of long-run matrix

LFrance/Germany 0.019970 0.00087944 0.026691 0.082659

LFrance 0.0042744 0.00018824 0.0057129 0.017692

LGermany 0.0047086 0.00020736 0.0062932 0.019490

Reduced form beta

LFrance/Germany -1.0000

LFrance -0.044039

LGermany 1.3365

Constant -4.1392

Standard errors of reduced form beta

LFrance/Germany 0.00000

LFrance 0.37250

LGermany 0.90508

Constant 2.2089

Moving-average impact matrix

-0.18798 16.848 4.7169

-0.62231 34.388 6.3657

-0.16115 13.738 3.7389

log-likelihood 2467.45781 -T/2log|Omega| 3280.50959

no. of observations 191 no. of parameters 105

rank of long-run matrix 1 no. long-run restrictions 0

beta is not identified

No restrictions imposed

LFrance/Germany: Portmanteau(12): 6.85112

LFrance : Portmanteau(12): 8.11577

LGermany : Portmanteau(12): 4.3378

LFrance/Germany: Normality test: Chi^2(2) = 33.424 [0.0000]**

LFrance : Normality test: Chi^2(2) = 38.314 [0.0000]**

LGermany : Normality test: Chi^2(2) = 3.1750 [0.2044]

LFrance/Germany: ARCH 1-7 test: F(7,142) = 1.1036 [0.3641]

LFrance : ARCH 1-7 test: F(7,142) = 0.12194 [0.9967]

LGermany : ARCH 1-7 test: F(7,142) = 0.44855 [0.8698]

LFrance/Germany: Hetero test: F(72,81) = 0.72380 [0.9184]

LFrance : Hetero test: F(72,81) = 0.70373 [0.9352]

LGermany : Hetero test: F(72,81) = 0.47543 [0.9992]

Vector Portmanteau(12): 58.9484

Vector Normality test: Chi^2(6) = 74.927 [0.0000]**

Vector Hetero test: F(432,463)= 0.60106 [1.0000]

SYS( 5) Estimating the system by OLS

The dataset is: new09.in7

The estimation sample is: 1974(4) - 1990(2)

URF equation for: LBelgium/Germany

Coefficient Std.Error t-value t-prob

LBelgium/Germany_1 1.24411 0.08057 15.4 0.0000

LBelgium/Germany_2 -0.429889 0.1303 -3.30 0.0012

LBelgium/Germany_3 0.242191 0.1348 1.80 0.0744

LBelgium/Germany_4 -0.0840452 0.1334 -0.630 0.5296

LBelgium/Germany_5 0.0963068 0.1260 0.764 0.4458

LBelgium/Germany_6 -0.184540 0.1258 -1.47 0.1446

LBelgium/Germany_7 0.102924 0.1285 0.801 0.4244

LBelgium/Germany_8 -0.0151956 0.1278 -0.119 0.9055

LBelgium/Germany_9 0.0137378 0.1228 0.112 0.9111

LBelgium/Germany_10 -0.0475944 0.1206 -0.395 0.6937

LBelgium/Germany_11 -0.0848517 0.1137 -0.746 0.4567

LBelgium/Germany_12 0.0888137 0.06890 1.29 0.1993

LBelgium_1 0.175739 0.1940 0.906 0.3664

LBelgium_2 -0.200036 0.2639 -0.758 0.4497

LBelgium_3 0.125802 0.2635 0.477 0.6337

LBelgium_4 -0.0591721 0.2655 -0.223 0.8239

LBelgium_5 0.160206 0.2678 0.598 0.5506

LBelgium_6 -0.228600 0.2653 -0.862 0.3902

LBelgium_7 -0.00589070 0.2654 -0.0222 0.9823

LBelgium_8 0.613126 0.2710 2.26 0.0250

LBelgium_9 -0.814964 0.2786 -2.93 0.0040

LBelgium_10 0.0607708 0.2843 0.214 0.8310

LBelgium_11 -0.0625811 0.2797 -0.224 0.8233

LBelgium_12 0.217344 0.1686 1.29 0.1992

LGermany_1 -0.373746 0.2162 -1.73 0.0859

LGermany_2 0.267891 0.3412 0.785 0.4336

LGermany_3 -0.00824147 0.3465 -0.0238 0.9811

LGermany_4 0.0151444 0.3493 0.0434 0.9655

LGermany_5 0.450110 0.3569 1.26 0.2092

LGermany_6 -0.376543 0.3550 -1.06 0.2905

LGermany_7 -0.351132 0.3493 -1.01 0.3164

LGermany_8 0.249408 0.3406 0.732 0.4651

LGermany_9 0.134627 0.3275 0.411 0.6816

LGermany_10 0.370252 0.3264 1.13 0.2584

LGermany_11 -0.204470 0.3263 -0.627 0.5319

LGermany_12 -0.0934401 0.2143 -0.436 0.6634

Constant -0.0804209 0.1089 -0.739 0.4613

sigma = 0.00614438 RSS = 0.00581402083

URF equation for: LBelgium

Coefficient Std.Error t-value t-prob

LBelgium/Germany_1 0.0564882 0.03530 1.60 0.1116

LBelgium/Germany_2 -0.0506352 0.05710 -0.887 0.3766

LBelgium/Germany_3 0.0121875 0.05907 0.206 0.8368

LBelgium/Germany_4 0.0364642 0.05844 0.624 0.5336

LBelgium/Germany_5 -0.0796239 0.05520 -1.44 0.1512

LBelgium/Germany_6 0.101231 0.05513 1.84 0.0683

LBelgium/Germany_7 -0.0832351 0.05629 -1.48 0.1413

LBelgium/Germany_8 0.0265802 0.05599 0.475 0.6356

LBelgium/Germany_9 -0.0570059 0.05381 -1.06 0.2911

LBelgium/Germany_10 0.0869395 0.05285 1.65 0.1020

LBelgium/Germany_11 -0.0532367 0.04982 -1.07 0.2870

LBelgium/Germany_12 0.0395195 0.03019 1.31 0.1924

LBelgium_1 0.951219 0.08498 11.2 0.0000

LBelgium_2 -0.140726 0.1156 -1.22 0.2255

LBelgium_3 -0.131885 0.1154 -1.14 0.2550

LBelgium_4 0.276431 0.1163 2.38 0.0187

LBelgium_5 -0.118454 0.1173 -1.01 0.3143

LBelgium_6 0.161914 0.1162 1.39 0.1656

LBelgium_7 -0.338599 0.1163 -2.91 0.0041

LBelgium_8 0.199237 0.1187 1.68 0.0953

LBelgium_9 0.0412499 0.1220 0.338 0.7358

LBelgium_10 -0.105923 0.1245 -0.850 0.3964

LBelgium_11 0.0981605 0.1225 0.801 0.4243

LBelgium_12 -0.00651130 0.07386 -0.0882 0.9299

LGermany_1 0.222759 0.09472 2.35 0.0199

LGermany_2 -0.293356 0.1495 -1.96 0.0515

LGermany_3 0.463101 0.1518 3.05 0.0027

LGermany_4 -0.370651 0.1531 -2.42 0.0166

LGermany_5 0.0287706 0.1564 0.184 0.8543

LGermany_6 1.07279e-005 0.1555 0.00 0.9999

LGermany_7 0.271382 0.1530 1.77 0.0781

LGermany_8 -0.00624830 0.1492 -0.0419 0.9667

LGermany_9 -0.128807 0.1435 -0.898 0.3707

LGermany_10 0.0195920 0.1430 0.137 0.8912

LGermany_11 -0.151840 0.1430 -1.06 0.2899

LGermany_12 0.0880479 0.09389 0.938 0.3498

Constant -0.229299 0.04770 -4.81 0.0000

sigma = 0.00269192 RSS = 0.001115951271

URF equation for: LGermany

Coefficient Std.Error t-value t-prob

LBelgium/Germany_1 -0.0362026 0.03033 -1.19 0.2344

LBelgium/Germany_2 0.0568306 0.04906 1.16 0.2485

LBelgium/Germany_3 0.0147421 0.05075 0.290 0.7718

LBelgium/Germany_4 -0.0108972 0.05021 -0.217 0.8285

LBelgium/Germany_5 -0.116697 0.04742 -2.46 0.0150

LBelgium/Germany_6 0.120452 0.04737 2.54 0.0120

LBelgium/Germany_7 -0.0318466 0.04837 -0.658 0.5112

LBelgium/Germany_8 -0.0253422 0.04810 -0.527 0.5991

LBelgium/Germany_9 0.0294442 0.04623 0.637 0.5252

LBelgium/Germany_10 -0.00683282 0.04541 -0.150 0.8806

LBelgium/Germany_11 -0.0270554 0.04281 -0.632 0.5283

LBelgium/Germany_12 0.0284262 0.02594 1.10 0.2748

LBelgium_1 0.0404842 0.07301 0.554 0.5801

LBelgium_2 -0.00894351 0.09935 -0.0900 0.9284

LBelgium_3 -0.168750 0.09917 -1.70 0.0909

LBelgium_4 0.288801 0.09992 2.89 0.0044

LBelgium_5 -0.238411 0.1008 -2.36 0.0193

LBelgium_6 0.133391 0.09987 1.34 0.1836

LBelgium_7 -0.105906 0.09988 -1.06 0.2907

LBelgium_8 -0.0980220 0.1020 -0.961 0.3380

LBelgium_9 0.289230 0.1049 2.76 0.0065

LBelgium_10 -0.164248 0.1070 -1.53 0.1268

LBelgium_11 -0.0314415 0.1053 -0.299 0.7656

LBelgium_12 0.0501439 0.06346 0.790 0.4306

LGermany_1 1.29590 0.08138 15.9 0.0000

LGermany_2 -0.311902 0.1284 -2.43 0.0163

LGermany_3 0.225749 0.1304 1.73 0.0855

LGermany_4 -0.310123 0.1315 -2.36 0.0196

LGermany_5 0.123547 0.1344 0.920 0.3592

LGermany_6 -0.224938 0.1336 -1.68 0.0943

LGermany_7 0.295004 0.1315 2.24 0.0263

LGermany_8 -0.103835 0.1282 -0.810 0.4192

LGermany_9 0.0448156 0.1233 0.364 0.7167

LGermany_10 -0.0346024 0.1229 -0.282 0.7786

LGermany_11 0.298141 0.1228 2.43 0.0164

LGermany_12 -0.274759 0.08066 -3.41 0.0008

Constant -0.0233588 0.04099 -0.570 0.5696

sigma = 0.00231282 RSS = 0.0008237694326

log-likelihood 2525.68367 -T/2log|Omega| 3338.73545

|Omega| 6.55862423e-016 log|Y'Y/T| -8.14095441

R^2(LR) 1 R^2(LM) 0.992103

no. of observations 191 no. of parameters 111

F-test on regressors except unrestricted: F(111,456) = 31811.5 [0.0000] **

F-tests on retained regressors, F(3,152) =

LBelgium/Germany_1 84.4832 [0.000]**LBelgium/Germany_2 4.84693 [0.003]**

LBelgium/Germany_3 1.19021 [0.315] LBelgium/Germany_4 0.302757 [0.823]

LBelgium/Germany_5 2.17739 [0.093] LBelgium/Germany_6 2.83358 [0.040]*

LBelgium/Germany_7 0.829163 [0.480] LBelgium/Germany_8 0.253797 [0.859]

LBelgium/Germany_9 0.740966 [0.529] LBelgium/Germany_10 1.08987 [0.355]

LBelgium/Germany_11 0.703625 [0.551] LBelgium/Germany_12 1.53880 [0.207]

LBelgium_1 47.3689 [0.000]** LBelgium_2 0.824504 [0.482]

LBelgium_3 1.08271 [0.358] LBelgium_4 3.50152 [0.017]*

LBelgium_5 1.88295 [0.135] LBelgium_6 1.02400 [0.384]

LBelgium_7 2.88040 [0.038]* LBelgium_8 3.81197 [0.011]*

LBelgium_9 5.08111 [0.002]** LBelgium_10 0.814791 [0.488]

LBelgium_11 0.339140 [0.797] LBelgium_12 0.857423 [0.465]

LGermany_1 87.0156 [0.000]** LGermany_2 2.45571 [0.065]

LGermany_3 3.33343 [0.021]* LGermany_4 2.87626 [0.038]*

LGermany_5 0.906398 [0.440] LGermany_6 1.52991 [0.209]

LGermany_7 2.15385 [0.096] LGermany_8 0.388259 [0.762]

LGermany_9 0.465400 [0.707] LGermany_10 0.483026 [0.695]

LGermany_11 3.39496 [0.020]* LGermany_12 5.56514 [0.001]**

Constant 8.75168 [0.000]**

correlation of URF residuals (standard deviations on diagonal)

LBelgium/Germany LBelgium LGermany

LBelgium/Germany 0.0061444 -0.16532 -0.11966

LBelgium -0.16532 0.0026919 0.34182

LGermany -0.11966 0.34182 0.0023128

correlation between actual and fitted

LBelgium/Germany LBelgium LGermany

0.99917 0.99996 0.99991

I(1) cointegration analysis, 1974(4) - 1990(2)

eigenvalue loglik for rank

2492.611 0

0.21606 2515.858 1

0.081106 2523.936 2

0.018136 2525.684 3

H0:rank<= Trace test [ Prob]

0 66.145 [0.000] **

1 19.651 [0.059]

2 3.4957 [0.504]

Asymptotic p-values based on: Restricted constant

Restricted variables:

[0] = Constant

Number of lags used in the analysis: 12

beta (scaled on diagonal; cointegrating vectors in columns)

LBelgium/Germany 1.0000 0.39584 0.030822

LBelgium -2.6147 1.0000 -0.57142

LGermany 3.1370 -1.8566 1.0000

Constant -5.2325 2.3655 -1.9104

alpha

LBelgium/Germany -0.027470 -0.078750 0.019827

LBelgium 0.040111 -0.010946 -0.0033899

LGermany 0.0018460 -0.016235 -0.012932

long-run matrix, rank 3

LBelgium/Germany LBelgium LGermany Constant

LBelgium/Germany -0.058031 -0.018254 0.079858 -0.080421

LBelgium 0.035674 -0.11389 0.14276 -0.22930

LGermany -0.0049789 -0.013672 0.023001 -0.023359

SYS( 6) Cointegrated VAR

The dataset is: new09.in7

The estimation sample is: 1974(4) - 1990(2)

Cointegrated VAR (12) in:

[0] = LBelgium/Germany

[1] = LBelgium

[2] = LGermany

Restricted variables:

[0] = Constant

Number of lags used in the analysis: 12

beta

LBelgium/Germany 1.0000

LBelgium -2.6147

LGermany 3.1370

Constant -5.2325

alpha

LBelgium/Germany -0.027470

LBelgium 0.040111

LGermany 0.0018460

Standard errors of alpha

LBelgium/Germany 0.015225

LBelgium 0.0064922

LGermany 0.0056482

Restricted long-run matrix, rank 1

LBelgium/Germany LBelgium LGermany Constant

LBelgium/Germany -0.027470 0.071826 -0.086175 0.14374

LBelgium 0.040111 -0.10488 0.12583 -0.20988

LGermany 0.0018460 -0.0048267 0.0057910 -0.0096593

Standard errors of long-run matrix

LBelgium/Germany 0.015225 0.039808 0.047761 0.079665

LBelgium 0.0064922 0.016975 0.020366 0.033970

LGermany 0.0056482 0.014768 0.017719 0.029554

Reduced form beta

LBelgium/Germany -1.0000

LBelgium 2.6147

LGermany -3.1370

Constant 5.2325

Standard errors of reduced form beta

LBelgium/Germany 0.00000

LBelgium 0.47463

LGermany 0.72964

Constant 1.0775

Moving-average impact matrix

1.3452 0.54091 8.2649

0.61395 -0.35713 16.896

0.082895 -0.47009 11.448

log-likelihood 2515.85803 -T/2log|Omega| 3328.90981

no. of observations 191 no. of parameters 105

rank of long-run matrix 1 no. long-run restrictions 0

beta is not identified

No restrictions imposed

LBelgium/Germany: Portmanteau(12): 5.96898

LBelgium : Portmanteau(12): 3.39841

LGermany : Portmanteau(12): 6.49229

LBelgium/Germany: Normality test: Chi^2(2) = 121.37 [0.0000]**

LBelgium : Normality test: Chi^2(2) = 6.3458 [0.0419]*

LGermany : Normality test: Chi^2(2) = 2.1111 [0.3480]

LBelgium/Germany: ARCH 1-7 test: F(7,142) = 0.42037 [0.8884]

LBelgium : ARCH 1-7 test: F(7,142) = 0.66839 [0.6985]

LGermany : ARCH 1-7 test: F(7,142) = 0.12698 [0.9963]

LBelgium/Germany: Hetero test: F(72,81) = 0.66325 [0.9616]

LBelgium : Hetero test: F(72,81) = 0.37190 [1.0000]

LGermany : Hetero test: F(72,81) = 0.49807 [0.9986]

Vector Portmanteau(12): 52.0286

Vector Normality test: Chi^2(6) = 120.49 [0.0000]**

Vector Hetero test: F(432,463)= 0.69746 [0.9999]

(4)AR

图acf 和Pasf

---- Maximum likelihood estimation of ARFIMA(4,0,0) model ----

The estimation sample is: 1973(5) - 1990(2)

The dependent variable is: DLFrance/Belgium

The dataset is: new09.in7

Coefficient Std.Error t-value t-prob

AR-1 0.382891 0.06996 5.47 0.000

AR-2 -0.0181099 0.07466 -0.243 0.809

AR-3 -0.0856939 0.07447 -1.15 0.251

AR-4 -0.0745809 0.06953 -1.07 0.285

Constant 0.00177940 0.0009659 1.84 0.067

log-likelihood 625.927726

no. of observations 202 no. of parameters 6

AIC.T -1239.85545 AIC -6.13789827

mean(DLFrance/Belgium) 0.00178439 var(DLFrance/Belgium) 0.000142048

sigma 0.0109093 sigma^2 0.000119013

BFGS using numerical derivatives (eps1=0.0001; eps2=0.005):

Strong convergence

Used starting values:

0.38482 -0.018468 -0.086797 -0.075880 0.0017844

---- Maximum likelihood estimation of ARFIMA(3,0,0) model ----

The estimation sample is: 1973(5) - 1990(2)

The dependent variable is: DLFrance/Belgium

The dataset is: new09.in7

Coefficient Std.Error t-value t-prob

AR-1 0.391643 0.06968 5.62 0.000

AR-2 -0.0169831 0.07482 -0.227 0.821

AR-3 -0.114939 0.06940 -1.66 0.099

Constant 0.00178156 0.001040 1.71 0.088

log-likelihood 625.354221

no. of observations 202 no. of parameters 5

AIC.T -1240.70844 AIC -6.142121

mean(DLFrance/Belgium) 0.00178439 var(DLFrance/Belgium) 0.000142048

sigma 0.0109409 sigma^2 0.000119704

BFGS using numerical derivatives (eps1=0.0001; eps2=0.005):

Strong convergence

Used starting values:

0.39367 -0.017166 -0.11667 0.0017844

---- Maximum likelihood estimation of ARFIMA(2,0,0) model ----

The estimation sample is: 1973(5) - 1990(2)

The dependent variable is: DLFrance/Belgium

The dataset is: new09.in7

Coefficient Std.Error t-value t-prob

AR-1 0.399155 0.07004 5.70 0.000

AR-2 -0.0633158 0.06988 -0.906 0.366

Constant 0.00178289 0.001164 1.53 0.127

log-likelihood 623.986982

no. of observations 202 no. of parameters 4

AIC.T -1239.97396 AIC -6.13848497

mean(DLFrance/Belgium) 0.00178439 var(DLFrance/Belgium) 0.000142048

sigma 0.0110163 sigma^2 0.000121359

BFGS using numerical derivatives (eps1=0.0001; eps2=0.005):

Strong convergence

Used starting values:

0.40113 -0.063965 0.0017844

---- Maximum likelihood estimation of ARFIMA(1,0,0) model ----

The estimation sample is: 1973(5) - 1990(2)

The dependent variable is: DLFrance/Belgium

The dataset is: new09.in7

Coefficient Std.Error t-value t-prob

AR-1 0.375174 0.06496 5.78 0.000

Constant 0.00178020 0.001239 1.44 0.152

log-likelihood 623.577387

no. of observations 202 no. of parameters 3

AIC.T -1241.15477 AIC -6.14433056

mean(DLFrance/Belgium) 0.00178439 var(DLFrance/Belgium) 0.000142048

sigma 0.0110389 sigma^2 0.000121857

BFGS using numerical derivatives (eps1=0.0001; eps2=0.005):

Strong convergence

Used starting values:

0.37701 0.0017844

Test for excluding: AR-1

Subset Chi^2(1) = 33.3597 [0.0000] **

Descriptive statistics for residuals:

Normality test: Chi^2(2) = 58.149 [0.0000]**

ARCH 1-1 test: F(1,198) = 7.5716 [0.0065]**

Portmanteau(36): Chi^2(35) = 47.627 [0.0755]

ARCH

ARCH coefficients:

Lag Coefficient Std.Error

1 0.14213 0.07377

2 0.15012 0.0743

3 0.16443 0.07515

4 -0.028656 0.07482

5 0.047427 0.07478

6 -0.039926 0.07482

7 -0.013674 0.07469

8 -0.011489 0.07465

9 0.029838 0.07458

10 -0.0027954 0.07309

11 -0.052836 0.07233

12 0.020861 0.07185

RSS = 1.47674e-005 sigma = 0.000289665

Testing for error ARCH from lags 1 to 12

ARCH 1-12 test: F(12,176) = 1.7613 [0.0579]

Residual [1973( 5) - 1990( 2)] saved to new09.in7

GARCH

VOL( 2) Modelling DLFrance/Belgium by restricted GARCH(1,1)

The dataset is: new09.in7

The estimation sample is: 1973(5) - 1990(2)

Coefficient Std.Error robust-SE t-value t-prob

Constant X 0.00137385 0.0005496 0.0006335 2.17 0.031

alpha_0 H 2.53091e-005 6.838e-006 1.225e-005 2.07 0.040

alpha_1 H 0.548753 0.1647 0.2417 2.27 0.024

beta_1 H 0.386169 0.1059 0.1239 3.12 0.002

log-likelihood 647.090499 HMSE 7.74626

mean(h_t) 0.000169302 var(h_t) 5.89695e-008

no. of observations 202 no. of parameters 4

AIC.T -1286.181 AIC -6.36723266

mean(DLFrance/Belgium) 0.00178439 var(DLFrance/Belgium) 0.000142048

alpha(1)+beta(1) 0.934922 alpha_i+beta_i>=0, alpha(1)+beta(1)<1

Initial terms of alpha(L)/[1-beta(L)]:

0.54875 0.21191 0.081834 0.031602 0.012204 0.0047127

0.0018199 0.00070278 0.00027139 0.00010480 4.0472e-005 1.5629e-005

Used sample mean of squared residuals to start recursion

Robust-SE based on analytical Information matrix and analytical OPG matrix

BFGS using analytical derivatives (eps1=0.0001; eps2=0.005):

Strong convergence

Used starting values:

0.0017844 2.1595e-005 0.70855 0.13943

Test for excluding: alpha_1

Subset Chi^2(1) = 11.0952 [0.0009] **

Using robust standard errors:

Subset Chi^2(1) = 5.15536 [0.0232] *

Portmanteau statistic for scaled residuals

Autocorrelation function (ACF) from lag 1 to 12:

0.24488 0.047178 -0.058108 -0.085325 -0.059613 -0.080555

-0.0051672 0.13997 0.19257 0.0078786 -0.13371 -0.15760

Partial autocorrelation function (PACF):

0.24488 -0.013605 -0.070740 -0.057554 -0.023454 -0.065465

0.024169 0.14067 0.12540 -0.091215 -0.13049 -0.078908

Portmanteau(12): Chi^2(12) = 38.040 [0.0002]**

Portmanteau statistic for squared scaled residuals

Autocorrelation function (ACF) from lag 1 to 12:

-0.011257 0.027938 -0.024482 0.032919 0.050857 -0.051928

-0.035495 -0.054797 0.075378 0.023350 -0.028213 0.0044665

Partial autocorrelation function (PACF):

-0.011257 0.027815 -0.023885 0.031675 0.052970 -0.053474

-0.038122 -0.051434 0.071194 0.027495 -0.027254 0.010154

Portmanteau(12): Chi^2(10) = 4.0149 [0.9467]

EGARCH

VOL( 3) Modelling DLFrance/Belgium by EGARCH(1,1)

The dataset is: new09.in7

The estimation sample is: 1973(5) - 1990(2)

Coefficient Std.Error robust-SE t-value t-prob

Constant X 0.00101843 0.0005399 0.0005579 1.83 0.069

alpha_0 H -1.41749 0.6391 0.9994 -1.42 0.158

eps[-1] H -0.143496 0.09108 0.1445 -0.993 0.322

|eps[-1]| H 0.691818 0.1431 0.2420 2.86 0.005

beta_1 H 0.833174 0.07042 0.1136 7.33 0.000

log-likelihood 649.124517 HMSE 8.68633

mean(h_t) 0.000159174 var(h_t) 4.75962e-008

no. of observations 202 no. of parameters 5

AIC.T -1288.24903 AIC -6.37747046

mean(DLFrance/Belgium) 0.00178439 var(DLFrance/Belgium) 0.000142048

Used sample mean of squared residuals to start recursion

Robust-SE based on numerical Hessian matrix and numerical OPG matrix

BFGS using numerical derivatives (eps1=0.0001; eps2=0.005):

Strong convergence

Used starting values:

0.0017844 1.0047 0.70855 0.00000 0.13943

(5) Forecast

Forecasting DLFrance/Belgium from 1990(3) to 1991(5)

Horizon Forecast (SE) Actual CondVar

1.0000 0.0010184 0.0051081 0.00013464 2.6093e-005

2.0000 0.0010184 0.0060643 -0.00097591 3.6775e-005

3.0000 0.0010184 0.0069962 0.0043737 4.8947e-005

4.0000 0.0010184 0.0078812 0.0029580 6.2113e-005

5.0000 0.0010184 0.0087034 -0.0045257 7.5749e-005

6.0000 0.0010184 0.0094536 0.0019288 8.9370e-005

7.0000 0.0010184 0.010128 -0.0019952 0.00010257

8.0000 0.0010184 0.010726 -0.0011920 0.00011505

9.0000 0.0010184 0.011251 0.0031894 0.00012660

10.000 0.0010184 0.011709 0.0056647 0.00013710

11.000 0.0010184 0.012104 .NaN 0.00014651

12.000 0.0010184 0.012443 .NaN 0.00015484

13.000 0.0010184 0.012734 .NaN 0.00016214

14.000 0.0010184 0.012980 .NaN 0.00016849

mean(Error) = -6.2387e-005 RMSE = 0.0030268

SD(Error) = 0.0030261 MAPE = 165.93

image1.png

FMBF computer lab1.pdf

FMBF: Computer Practical 1

Introduction

There are four workshops for the FMBF module this term which will be organised as

follows:

Practical 1 ARIMA modelling and unit root testing.

Practical 2 Cointegration procedures.

Practical 3 ARCH/GARCH modelling and forecasting.

1 ARIMA Modelling

1.1 Aims

In the first part of this session we will firstly load a dataset and experiment with ARIMA

modelling. Once the concept has been demonstrated you will be required to find a preferred

model for the stock price data that we will be using. The stock price series is raw data so you

will need to calculate returns yourself using the calculator function in PcGive.

We will demonstrate the procedure for using the Time Series Models package in PcGive by

estimating an AR(1) model:

1.2 Key Steps

Importing and transforming the data

1. We will be using monthly data on the price of British Airways from 1996 to 2002.

Download the file BA.xls from duo that contains these data.

2. Start PcGive.

(Start > Search PcGive12)

3. Create new database in PcGive.

(File > New… > OxMetrics (Data: *.in7) > Frequency: Monthly > Observations: 74 > OK).

Practical 4 Review.

4. Copy the price data column from Excel to PcGive. Double click on the first row and type

the column title: BA.

Note: You could also click File > Open data file... and import the Excel file directly.

However, PcGive will not automatically recognise the dates in the leftmost column. If you

chose to do it this way you could choose Edit > Change Sample to let PcGive know we are

dealing with monthly data from 1996.

5. Use Calculator to calculate the log return, i.e., generate new series Ri which equals the

dlog of BA.

Prior to constructing the model

You should plot and carefully examine the ACF and PACF. Recall that we plotted the ACF

and PACF last term, and that you can do this by going to the Graphics button in PcGive.

(Graphics > Choose the variables and click All plot types > Time-series properties > In

Dynamic Properties tick ACF and PACF and click OK)

Is a particular model suggested by this graphical analysis?

Constructing the model

These steps show the construction of an AR(1) model for demonstration.

1 In PcGive select Model > Category: Models for time series data > Model class: ARFIMA

models using PcGive.

2 Select Formulate…

3 Select Ri as the dependent variable (Y), add a constant term (PcGive should do this

automatically), and press OK.

4 Set AR order as 1 and fix the Fractional parameter d at 0. Treatment of the mean should

automatically be set to None (or using constant as regressor).

5 Press OK, and select Maximum Likelihood.

6 Press OK and the Estimation Results will appear.

7 Examine the results. Is this model satisfactory?

Exercice 1: Identifying your preferred model

Carefully examine the results from your model. You should:

 Check the residuals to see if they conform to white noise using ACF and PACF and the Q-

statistic (Ljung Box statistic).

 Re-estimate the model, overfitting in an effort to isolate the preferred specification.

 You may then want to utilise the AIC when choosing between competing models.

If you are not prompted to do so by the steps above, you should at the least estimate an MA(1)

and an ARIMA(1,0,1) model to be clear on the procedure of specifying such models in

PcGive.

2 Unit root testing

2.1 Aims

In the second part of this session we will examine stationarity testing using PcGive.

Price/Earnings data for the US will be used to demonstrate how the software can easily test

for the presence of a unit root and display results in a fashion that easily allows us to choose a

preferred model cf. the number of lags to include. We will then test for stationarity in

monthly data for the FTSE 100 and FTSE All Share.

Example 1: Annual Price/Earnings Ratio

This example is based on the illustration of the annual price/earnings ratio proposed in

Verbeek (2004, p.274). The literature has focussed on whether the price/earnings ratio is

mean reverting (why might this be interesting?).

1 Load the data PE.xls into PcGive (File > Open… > PE.xls). This is annual data on the

ratio of the S&P Composite Stock Price Index and S&P Composite Earnings. The sample

(annual data) runs from 1871 to 2002.

2 Plot the log of the series (LOGPE) using GiveWin graphics (Graphics > Choose LOGPE >

Actual series) . Does it look stationary?

3 We will test for stationarity with the standard Dickey-Fuller regression, i.e. if we denote

the log P/E ratio as Yt

1 1t t tY Y      (1)

Note that you will need to use Calculator to diff the LOGPE series.

Modelling this using Single equation dynamic modelling... gives

10.335 0.125t t tY Y e    (2)

(Model > Category: Model for time-series data > Model class: Single-equation Dynamic

Modelling using PcGive > Formulate… > Select DLOGPE as Y and choose lagged

LOGPE > Click OK)

The full output from PcGive is

We can calculate the DF test statistic as -2.57, the 5% critical value being -2.88. Thus we

cannot reject the null of a unit root. However, for this result to hold we must have included

lags to the extent that the error term is white noise.

2.2 Automated unit root testing

Fortunately, PcGive makes it easy to perform unit root testing automatically, saving us

having to run a regression each time. It also produces a neat summary table allowing easy

selection of the appropriate number of lag terms.

We will first replicate the results previously obtained:

1 Select Model > Category: Other models > Model class: Descriptive Statistics using

PcGive)

2 Select Formulate

3 Add LOGPE to the model and click OK

4 In Descriptive Statistics select Unit-root tests, and then edit Unit-root test settings so that

Lag length for differences is 0 and Constant) is selected

5 Click OK and then OK in the Estimate Model dialog

6 The following results should appear in the Results area in GiveWin

These are the results we obtained previously. Note that the software automatically calculates

the correct test statistic and critical value.

2.3 ADF testing

We will now add lags and look at the results from augmented Dickey-Fuller tests:

1 Formulate a new model (Descriptive Statistics)

2 Edit Unit-root test settings so that Lag length for differences is 6 and Constant) is selected.

Make sure that Report summary table only is selected.

The following results are presented

There is a rejection of the null of a unit root at the 5% level with one lag. However, none of

the other ADF tests reject the null of nonstationarity. Does this concur with the graphical plot

of the P/E series that you produced above?

Exercice 2: Annual Price/Earnings Ratio cont...

Test for the presence of a second unit root in annual price/earnings data (Hint: you will need

to difference the data once more). Can you reject the null of nonstationarity? What

conclusion does this lead you towards?

Exercice 3: Stationarity in the FTSE 100 and ALL SHARE

1. Load the data FTSEDATA.xls that is on duo. This contains monthly data for the FTSE 100

and ALL SHARE from 1985:1.

2. Create logarithms of the two indices, naming them LFTSE100 and LFTALLSH.

3. Plot the series then test for stationarity adding an appropriate number of lags.

4. Create the first difference of LFTSE100 and LFTALLSH and test for stationarity after

plotting the differenced series.

5. Come to conclusions about the presence of a unit root in the two series.

2.4 Points to note

 Make sure you are clear on what the columns in the tables of unit root test output mean;

see Figure 1 and Figure 2.

 Perron procedure (not Perron's test) may be used to test for unit root in ammore systematic

way (see Harris and Sollis p. 47 and your lecture notes). This will not be considered here.

References

M. Verbeek. A Guide to Modern Econometrics. John Wiley & Sons, Inc., 2004.

Figure 1: Interpreting unit root test output: summary table option

Figure 2: Interpreting unit root test output: summary table vs. standard output

Guide_to_ACF_PACF_plots(computer lab1).pdf

Guide to ACF/PACF Plots

The plots shown here are those of pure or theoretical ARIMA processes. Here are some general guidelines for identifying the process:

Nonstationary series have an ACF that remains significant for half a dozen or more lags, rather than quickly declining to zero. You must difference such a series until it is stationary before you can identify the process.

Autoregressive processes have an exponentially declining ACF and spikes in the first one or more lags of the PACF. The number of spikes indicates the order of the autoregression.

Moving average processes have spikes in the first one or more lags of the ACF and an exponentially declining PACF. The number of spikes indicates the order of the moving average.

Mixed (ARMA) processes typically show exponential declines in both the ACF and the PACF.

At the identification stage, you do not need to worry about the sign of the ACF or PACF, or about the speed with which an exponentially declining ACF or PACF approaches zero. These depend upon the sign and actual value of the AR and MA coefficients. In some instances, an exponentially declining ACF alternates between positive and negative values.

ACF and PACF plots from real data are never as clean as the plots shown here. You must learn to pick out what is essential in any given plot. Always check the ACF and PACF of the residuals, in case your identification is wrong. Bear in mind that:

Seasonal processes show these patterns at the seasonal lags (the multiples of the seasonal period).

1

2

You are entitled to treat nonsignificant values as zero. That is, you can ignore values that lie within the confidence intervals on the plots. You do not have to ignore them, however, particularly if they continue the pattern of the statistically significant values.

An occasional autocorrelation will be statistically significant by chance alone. You can ignore a statistically significant autocorrelation if it is isolated, preferably at a high lag, and if it does not occur at a seasonal lag.

Consult any text on ARIMA analysis for a more complete discussion of ACF and PACF plots.

ARIMA(0,0,1), θ>0

ACF PACF

3

Guide to ACF/PACF Plots

ARIMA(0,0,1), θ<0

ACF PACF

ARIMA(0,0,2), θ1θ2>0

ACF PACF

4

ARIMA(1,0,0), φ>0

ACF PACF

ARIMA(1,0,0), φ<0

ACF PACF

5

Guide to ACF/PACF Plots

ARIMA(1,0,1), φ<0, θ>0

ACF PACF

ARIMA(2,0,0), φ1φ2>0

ACF PACF

6

ARIMA(0,1,0) (integrated series)

ACF

  • Table of Contents
  • 1. Guide to ACF/PACF Plots
  • Index

FMBF computer lab2.pdf

FMBF: Computer Practical 2

Introduction

This workshop session covers cointegration, using the Engle-Granger and Johansen

approaches. You should be aware of the benefits and drawbacks of each approach.

1 Engle-Granger

Exercise 1: Cointegration between the S&P and FTSE All-Share

1. Load the data file FMBF Prac2.xls from duo. This contains monthly data on the

S&P 500 and FTSE All Share from January 1 1965 to January 1 2004.

2. Log both series (Calculator) and then use the unit root testing facility in

Descriptive Statistics to assess the degree of integration of the series (Model >

Category: Other models; Model class: Descriptive statistics using PcGive).

Notes: most financial variables are I(1) series. To conduct the EG procedure, we

should firstly check whether the two time series are I(1).

3. Regress LS&P on LFTSE and a constant using OLS (Model > Category:

Models for time-series data; Model class: Single-equation dynamic

Modelling using PcGive).

4. Save the cointegration regression residual in the database (Test > Test Menu:

Store Residuals etc. in Database… > Store in database: Residuals).

5. Test for cointegration by performing a unit-root test on the saved residuals (do

not include deterministic components here).

6. Evaluate the results and establish whether or not the series cointegrate (note:

make sure you use the correct critical values).

7. If appropriate, build an ECM. Do this by regressing DLS&P on a constant,

DLFTSE and the one-period lagged residuals that were previously stored in the

database. Interpret your findings.

Notes: according to the unit root test of the residuals, since the residuals are not

stationary, it is not appropriate to put the non-stationary residuals into the ECM.

In other words, the residuals are I(1). Therefore, we should estimate a model

containing only first differences.

2 Johansen

Example 1: Long-run PPP

This is a PcGive implementation of the long-run purchasing power parity example

presented in Verbeek (2004, p.331). We begin by loading the data file ppp.xls from

duo, which contains monthly observations from 1981:1 to 1996:6 on price indices and

exchange rates from France and Italy. The variables contained in the file are as

follows:

This example investigates the concept of PPP, where exchange rate equals the ratio of

price levels. In logarithms, we represent PPP as:

*

ttt pps  (1)

where ts is the log of the spot exchange rate, tp

is the log of domestic prices and

*

tp is the log of foreign prices.

1. Following Verbeek's reasoning we will first run a test with p = 3, excluding a

time trend (Model > Category: Models for time-series data; Model class:

Multiple-equation dynamic Modelling using PcGive). Note that PcGive

automatically restricts the Constant term (shown by the U to its left. We remove

this to restrict the constant following Verbeek's example. Select U Constant in

Selection > Change Use default status to Clear status and click Set, then the

U is removed. Note that this now corresponds to Model 2 in the Pantula

Principle). Click OK and choose Unrestricted system.

2. Press Test > Test Menu: Dynamic Analysis and Cointegration Tests... >

Dynamic Analysis: I(1) cointegration analysis > OK. You are presented with

results, the firrst part of which are the eigenvalues:

We can see from the results that there are two small eigenvalues that are significant at

the 1 percent level. In this case we reject H0 : r = 0 and also H0 : r = 1, but we cannot

reject H0 : r = 2 against the alternative of H1 : r = 3. Therefore using Johansen we

conclude that there are two cointegrating relationships. P-values are based on Doornik

(1998) (reprinted in McAleer and Oxley (1999)). Verbeek (2004, p.332) reminds us

that in this particular example, Engle-Granger finds that the null of no cointegration

could not be rejected. (Note: you can follow the E-G procedure that was used above to

verify this). One possible explanation is that the number of lags is too small.

Therefore we formulate a model with p = 12, supported by the use of monthly data:

These results are clearly weaker than with p = 3. We do, however, have a rejection of

H0 : r = 1. We can now move on to build a cointegrated VAR model. We will assume

r = 1.

3. Formulate the model used for estimating the cointegration test for p = 12.

Remember that we have a restricted constant (Model > Category: Models for

time-series data; Model class: Multiple-equation dynamic Modelling using

PcGive).

4. Click OK and then select Cointegrated VAR and press OK once more.

5. In the Cointegrated VAR Settings dialog box make sure the Cointegrating rank is

set to 1. Click OK and OK to estimate a Reduced Rank Regression

You should be presented with the following output in the Results:

The most interesting part of these results, relating to estimating the cointegrating

vector, β, are shown under Reduced form beta. The normalized cointegrating

therefore corresponds to:

*756.14346.6 ttt pps  (2)

As Verbeek, p.332 points out, this “does not seem to correspond to an economically

interpretable long-run relationship.”

3 The Pantula Principle

Following Johansen (1992) we can use the so-called Pantula Principle to determine

the choice for deterministic components in the cointegration space and/or the

short-run, and also establish the order of the cointegration rank r. Recall that we

estimate all three models and present the results from the r = 0 (model 2, the most

restrictive) to r = n-1 (model 4, the least restrictive). Moving through these models

and examining them in turn, we look to the trace statistic and stop once the null

hypothesis cannot be rejected. In the case of the example we are concerned with

identifying the deterministic components. One further point to consider are the correct

critical values for models 1 to 4.

Exercice 2: The Pantula Principle

In the above worked example we estimated a long-run PPP model and tested for

cointegration. Effectively, what we did corresponds with Model 2 in the Pantula

Principle.

 You should now follow this principle, estimating Models 2, 3 and 4 in sequence.

You should examine your results and establish which specification is preferred.

To assist you, Table 1 contains pointers on setting up each model in PcGive. It is

helpful to construct a table similar to Table 5.5 in Harris and Sollis (2003).

 In the example, we estimated with both 3 lags and 12 lags. You should come to

your own conclusion about this by first looking at appropriate graphic analysis.

Specifically you can go to Test > Graphic Analysis and look at Actual and

fitted values, Cross plot of actual and fitted, Residuals (scaled), Residual

density and histogram (kernel estimate) and Residual correlogram (ACF).

 System reduction is important in our goal to find the preferred model. You should

examine F-tests on the retained regression to see if it is possible to delete all the

lags of the same length (i.e. those that are not significant) whilst keeping the

sample period unchanged. You can use Test > Exclusion Restrictions... to

evaluate.

 Estimate your preferred model as a cointegrated VAR.

 As usual, diagnostic tests are important. See Test > Test Summary for

equation-by-equation and system-wide tests, which you should examine.

3.1 Imposing Restrictions

We can test for restrictions on α and β with PcGive. For example, to test the

restriction

  0,0, . (3)

We would go to Model > Category: Models for time-series data; Model class:

Multiple-equation dynamic Modelling using PcGive and select Cointegrated VAR.

Press OK and enter a Cointegrating rank of 1. We then select General restrictions

and press OK.

The General Restrictions dialog box opens, where we specify the restriction in the

form &1=0;&2=0;&3=0 - see Figure 2 for a screenshot. We are testing a null of

weakly exogenous - you may wish to try this for the PPP model estimated above.

We can also use PcGive's ability to impose general restrictions to test for unique

cointegrating vectors and in addition jointly test restrictions on α and β. See Harris

and Sollis (2003, p.135-163) for full details, examples and references to imposing

restrictions in PcGive.

4 Points to note

 Make sure you are clear about the differences between the E-G and Johansen

approaches to cointegration.

 In the example above we used the trace test. This evaluates whether the smallest k

- r0 eigenvalues significantly differ from 0. However, we can also use the

maximum eigenvalue test. This tests H0 : r ≤ r0 against H1 : r = r0 + 1. PcGive

gives the eigenvalues so it is possible to calculate these. For example, in the PPP

example the first eigenvalue is 0.30091 so the axm statistic can be calculated

as 183*LN(1-0.30091), i.e. 65.509 which can be set against the correct critical

value, in this case 22.04.

References

J. A. Doornik. Approximations to the asymptotic distribution of cointegration tests.

Journal of Economic Surveys, 12:573{593, 1998.

R. Harris and R. Sollis. Apple Time Series Modelling and Forecasting. John Wiley &

Sons Ltd., Chichester, 2003.

D. F. Hendry and J. A. Doornik. Empirical Econometric Modelling Using Pc-Give,

volume 1. Timberlake Consultants Ltd., 3 edition, 2001.

S. Johansen. Cointegration in partial systems and the effciency of single equation

analysis. Journal of Econometrics, 52:389{402, 1992.

M. McAleer and L. Oxley. Practical Issues in Cointegration Analysis. Blackwell

Publishers, Oxford, 1999.

M. Verbeek. A Guide to Modern Econometrics. John Wiley & Sons, Inc., 2004.

Johansen Test by PcGive(computer lab2).pdf

— Appendix ————-—

Cointegration Analysis Using the Johansen Technique: A Practitioner's

__ Guide to PcGive 10.1

This appendix provides a basic introduction on how to implement the Johan- sen technique using the PcGive 10.1 econometric program (see Doornik and Hendry, 2001 for full details). Using the same data set as underlies much of the analysis in Chapters 5 and 6, we show the user how to work through Chapter 5 up to the point of undertaking joint tests involving restrictions on a and p.

This latest version of PcGive brings together the old PcGive (single equa- tion) and PcFiml (multivariate) stand-alone routines into a single integrated software program (that in fact is much more than the sum of the previous versions, since it is built on the Ox programming language and allows various bolt-on Ox programs to be added—such as dynamic panel data analysis (DPD), time series models and generalized autoregressive conditional heteroscedastic (GARCH) models—see Chapter 8). It is very flexible to operate, providing drop-down menus and (for the present analysis) an extensive range of modelling features for 7(1) and 7(0) systems (and limited analysis of the 7(2) system).1 Cointegration facilities are embedded in an overall modelling strategy leading through to structural vector autoregression (VAR) modelling.

After the data have been read-in to GiveWin2 (the data management and graphing platform that underpins PcGive and the other programs that can operate in what has been termed the Oxmetrics suite of programs), it is first necessary to (i) start the PcGive module, (ii) select 'Multiple-equation Dynamic Modelling' and then (iii) 'Formulate' a model. This allows the user to define the model in (log) levels, fix which deterministic variables should enter the co- integration space, determine the lag length of the VAR and decide whether

1 PcGive also allows users to run batch jobs where previous jobs can be edited and rerun. 2 The program accepts data files based on spreadsheets and unformatted files.

260 APPENDIX

Figure A.I. Formulating a model in PcGive 10.1: Step (1) choosing the correct model option.

7(0) variables, particularly dummies, need to be specified to enter the model in the short-run dynamics but not in the cointegration spaces (see Figures A. 1 and A.2).

When the 'Formulate' option is chosen, the right-hand area under 'Data- base' shows the variables available for modelling. Introducing dummies and transformations of existing variables can be undertaken using the 'Calculator' or 'Algebra Editor' under Tools' in GiveWin, and these new variables when created will also appear in the 'Database'. In this instance, we will model the demand for real money (rm) as a function of real output (y), inflation (dp) and the interest rate (rstar), with all the variables already transformed into log levels. The lag length (k) is set equal to 4 (see lower right-hand option in Figure A.2); if we want to use an information criterion (1C) to set the lag length, then k can be set at different values, and when the model is estimated it will produce the Akaike, Hannan—Quinn and Schwarz 1C for use in deter- mining which model is appropriate.3 (However, it is also necessary to ensure that the model passes diagnostic tests with regard to the properties of the residuals of the equations in the model—see below—and therefore use of an 1C needs to be done carefully.)

Each variable to be included is highlighted in the 'Database' (either one at a time, allowing the user to determine the order in which these variables enter, or all variables can be simultaneously highlighted). This will bring up an '<<Add' option, and, once this is clicked on, then the model selected appears on the left-hand side under 'Model'. The 'Y' next to each variable indicates

3 Make sure you have this option turned on as it is not the default. To do this in PcGive. choose 'Model', then 'Options', 'Additional output' and put a cross in the information criterion box.

APPENDIX , 261

Figure A.2. Formulating a model in PcGive 10.1: Step (2) choosing the 'Formulate' option.

that it is endogenous and therefore will be modelled, a 'IT indicates the vari- able (e.g., the Constant, which enters automatically) is unrestricted and will only enter the short-run part of the vector error correction model (VECM), and the variables with '_k' next to them denote the lags of the variable (e.g., rm t–1).

We also need to enter some dummies into the short-run model to take account of'outliers' in the data (of course we identify these only after estimating the model, checking its adequacy, and then creating deterministic dummies to try to overcome problems; however, we shall assume we have already done this,4

4 In practice, if the model diagnostics—see Figure A.3—indicates, say, a problem of non-normality in the equation determining a variable, plot the residuals using the graphing procedures (select, in PcGive, 'Test' and 'Graphic analysis' and then choose 'Residuals' by putting a cross in the relevant box). Visually locate outliers in terms of when they occur, then again under 'Test' choose 'Store residuals in database', click on residuals and accept the default names (or choose others) and store these residuals in the spreadsheet. Then go to the 'Window' drop-down option in Give Win and select the database, locate the residuals just stored, locate the outlier residuals by scrolling down the spreadsheet (using the information gleaned from the graphical analysis) and then decide how you will 'dummy out' the outlier (probably just by creating a dummy variable using the 'Calculator' option in Give Win, with the dummy being 0 before and after the outlier date and 1 for the actual date of the outlier).

262 APPENDIX

or that ex ante we know such impacts have occurred and need to be included). Hence, highlight these (dumrst, dumdp, dumdpl), set the lag length option at the bottom right-hand side of the window to 0 and then click on '<Add'. Scroll down the 'Model' window, and you will see that these dummies have 'Y' next to them, which indicates they will be modelled as additional variables. Since we only want them to enter unrestrictedly in the short-run model, select/highlight the dummies and then in the 'Status' options on the left-hand side (the buttons under 'Status' become available once a variable in the model is highlighted) click on 'Unrestricted', so that each dummy now has a 'U' next to it in the model.

Finally, on the right-hand side of the 'Data selection' window is a box headed 'Special'. These are the deterministic components that can be selected and added to the model. In this instance, we select 'CSeasonal (centred seasonal dummies), as the data are seasonally unadjusted, and add the seasonal dummies to the model. They automatically enter as unrest- ricted. Note that if the time 'Trend' is added, it will not have a 'U' next to it in the model, indicating it is restricted to enter the cointegration space (Model 4 in Chapter 5—see equation (5.6)). If we wanted to select Model 2 then we would not enter the time trend (delete it from the model if it is already included), but would instead click on 'Constant' in the 'Model' box and click on 'Clear' under the 'Status' options. Removing the unrest- ricted status of the constant will restrict it to enter the cointegration space. Thus, we can select Models 2–4, one at a time, and then decide which deterministic components should enter II, following the Pantula principle (see Chapter 5).

Having entered the model required, click OK, bringing up the 'Model settings' window, accept the default of 'Unrestricted system' (by clicking OK again) and accept ordinary least squares (OLS) as the estimation method (again by clicking OK). The results of estimating the model will be available in Give Win (the 'Results' window—accessed by clicking on the Give Win toolbar on your Windows status bar). Return to the PcGive window (click on its toolbar), choose the 'Test' option to activate the drop-down options, and click on 'Test summary'. This produces the output in GiveWin as shown in Figure A.3. The model passes the various tests equation by equation and by using system-wide tests.

Several iterations of the above steps are likely to be needed in practice to obtain the lag length (k) for the VAR, which deterministic components should enter the model (i.e., any dummies or other 7(0) variables that are needed in the short-run part of the VECM to ensure the model passes the diagnostic tests on the residuals) and which deterministic components should enter the cointegration space (i.e., should the constant or trend be restricted to be included in II). To carry out the last part presumes you have already tested for the rank of II, so we turn to this next.

To undertake cointegration analysis of the I(1) system in PcGive, choose Test', then 'Dynamic Analysis and Cointegration tests' and check the "7(1)

APPENDIX

rm Y dp rstar rm Y dp rstar rm Y dp rstar rm y dp rstar rm y dp rstar

263

Portmanteau(11): Portmanteau(11) : Portmanteau(11): Portmanteau(11) : AR 1-5 test: AR 1-5 test: AR 1-5 test: AR 1-5 test: Normality test: Normality test: Normality test: Normality test: ARCH 1-4 test: ARCH 1-4 test: ARCH 1-4 test: ARCH 1-4 test: hetero test: hetero test: hetero test: hetero test:

11.2164 6.76376 3.66633 11.6639 F(5, F(5, F(5, F(5, Chi' Chi- Chi' Chi' F(4, F(4, F(4, F(4, F(35 F(35 F(35 F(35

73) 73) 73) 73) 2(2) 2(2) 2(2) 2(2) 70) 70) 70) 70) ,42) ,42) ,42) ,42)

1 1 1 1 2 5 4 o

— 1

= 1 -I

- 0. = 0. = 0. = 0. - 0.

.4131

.8569

.0269

.8359

.8297

.0521

.6973

.7019

.5882

.1669

.1133 68023 38980 72070 67314 88183

[0. [0. [0. [0. [0. [0. [0. [0. [0. [0. [0. [0. [0. [0. [0. [0.

2297] 1125] 4083] 1164] 2430] 0800] 0955] 2590] 1871] 3329] 3573] 6080] 9974] 8385] 8838] 6463]

Vector Portmanteau(ll): 148.108 Vector AR 1-5 test: F(80,219)= 1.0155 [0.4555] Vector Normality test: Chi'2(8) = 15.358 [0.0525] Vector hetero test: F(350,346)= 0.47850 [1.0000] Not enough observations for hetero-X test

Figure A.3. Estimating the unrestricted VAR in PcGive 10.1; model diagnostics.

cointegration analysis' box.5 The results are produced in Figure A.4,6 provid- ing the eigenvalues of the system (and log-likelihoods for each cointegration rank), standard reduced rank test statistics and those adjusted for degrees of freedom (plus the significance levels for rejecting the various null hypotheses) and full-rank estimates of a, p and IT (the P are automatically normalized along the principal diagonal). Graphical analysis of the (J-vectors (unadjusted and adjusted for short-run dynamics) are available to provide a visual test of which vectors are stationary,7 and graphs of the recursive eigenvalues associated with each eigenvector can be plotted to consider the stability of the cointegration vectors.8

5 Note that the default output only produces the trace test. To obtain the A-max test as well as the default (and tests adjusted for degrees of freedom), in PcGive choose 'Model', then 'Options', 'Further options' and put a cross in the box for cointegration test with Max test. 6 Note that these differ from Box 5.5 and Table 5.5, since the latter are based on a model without the outlier dummies included in the unrestricted short-run model. 7 The companion matrix that helps to verify the number of unit roots at or close to unity, corresponding to the 7(1) common trends, is available when choosing the 'Dynamic analysis' option in the 'Test' model menu in PcGive. 8 Note that, to obtain recursive options, the 'recursive estimation' option needs to be selected when choosing OLS at the 'Estimation Model' window when formulating the model for estimation.

264 APPENDIX 1(1) cointegration analysis, 1964 (2) to 1989 (2)

eigenvalue

0.57076 0.11102 0.063096 0.0020654

loglik for rank 1235.302 0 1278.012 1 1283.955 2 1287.246 3 1287.350 4

rank Trace test [ Prob] Max test [ Prob] Trace test [T-nm] Max test [T-nm] 0 104.10 [0.000]** 85.42 [0.000]** 87.61 [0.000]** 71.89 [0.000]' 1 18.68 [0.527] 11.89 [0.571] 15.72 [0.737] 10.00 [0.747] 2 6.79 [0.608] 6.58 [0.547] 5.72 [0.731] 5.54 [0.676] 3 0.21 [0.648] 0.21 [0.648] 0.18 [0.675] 0.18 [0.675]

Asymptotic p-values based on: Unrestricted constant Unrestricted variables: [0] = Constant [1] = CSeasonal [2] = CSeasonal_l [3] = CSeasonal_2 [4] = dumrst [5] = dumdp [6] = dumdp1 Number of lags used in the analysis: 4

beta (scaled on diagonal; cointegrating vectors in columns) rm y dp rstar

1.0000 -1.0337 6.4188 6.7976

15.719 1.0000 -207.49 131.02

-0.046843 0.064882 1.0000

-0.039555

1.6502 -0.13051 8.6574 1.0000

alpha rm -0.18373 y -0.0081691 dp 0.022631 rstar 0.0046324

0.00073499 -0.0010447 0.00023031 -0.0011461

0.0012372 -0.16551

-0.042258 -0.0022919

-0.0010530 -0.00080063 0.0010822 0.0018533

long-run matrix, rank 4 rm y

rm -0.17397 0.19088 y -0.018159 -0.0032342 dp 0.030017 -0.026047 rstar -0.010218 -0.0063252

dp -1.3397

-0.0081182 0.064590 0.28129

rstar -1.1537 -0.18666 0.18677 -0.11673

Figure A.4. 7(1) cointegration analysis in PcGive 10.1.

After deciding on the value of r < n, it is necessary to select a reduced rank system. In PcGive, under 'Model', choose 'Model settings' (not 'Formulate'), select the option 'Cointegrated VAR' and in the window that appears set the cointegration rank (here we change '3' to '1', as the test statistics indicate that r — 1). Leave the 'No additional restrictions' option unchanged as the default, click OK in this window and the next, and the output (an estimate of the new value of II together with the reduced-form cointegration vectors) will be written to the results window in GiveWin.

Finally, we test for restrictions on a and p (recall that these should usually be conducted together). To illustrate the issue, the model estimated in Chapter 6

APPENDIX , , 265

Figure A.5. Testing restrictions on a and B using 'General Restrictions' in PcGive 10.1.

is chosen (instead of the one above) with a time trend restricted into the cointegration space and r — 2. Thus, we test the following restrictions:

, r-i i * * o [ 0 — 1 * * *

,_ r* o * o ~~ L* o * o

using the option 'General restrictions'. To do this in PcGive, under 'Model', choose 'Model settings', select the option 'Cointegrated VAR' and in the window that appears set the cointegration rank (here we change '3' to '2', since we have chosen r = 2). Click the 'General restrictions' option, type the relevant restrictions into the window (note that in the 'Model' the parameters are identified by '&' and a number—see Figure A.5), click OK in this window (and the next) and the results will be written into Give Win (Figure A.6—see also the top half of Box 6.1).

CONCLUSION

For the applied economist wishing to estimate cointegration relations and then to test for linear restrictions, PcGive 10.1 is a flexible option. But there are others. Harris (1995) compared three of the most popular options available in the 1990s (Microfit 3.0, Cats (in Rats) and PcFiml—the latter the predecessor to the current PcGive). The Cats program9 has seen little development since its 9 Cointegration Analysis of Times Series (Cats in Rats), version 1.0, by Henrik Hansen and Katrina Juselius, distributed by Estima.

266 APPENDIX

Cointegrated VAR (4) in: [0] - rm tl] = y [2] = dp [3] = rstar Unrestricted variables: [0] = dumrst [1] = dumdp [2] = dumdp 1 [3] = Constant [4] = CSeasonal [5] = CSeasonal_l [6] = CSeasonal_2 Restricted variables: [0] = Trend Number of lags used in the analysis: 4

General cointegration restrictions: &8=-l;&9=l;&12=0; &13=0;&14=-1; &2=0;&3=0;&6=0;&7=0;

beta rm y dp rstar Trend

-1.0000 1.0000 -6.5414 -6.6572 0.00000

0.00000 -1.0000 2.8091 -1.1360

0.0066731

Standard errors of beta rm y dp rstar Trend

alpha rm y dp rstar

0.00000 0.00000 0.88785 0.33893 0.00000

0.17900 0.00000

-0.011637 0.00000

0.00000 0.00000 0.46671 0.19346

0.00020557

0.083003 0.00000 -0.15246 0.00000

Standard errors of alpha rm 0.018588 0.074038 y 0.00000 0.00000 dp 0.0078017 0.031076 rstar 0.00000 0.00000

log—likelihood 1290.6274 -T/2log|Omega| 1863.87857 no. of observations 101 rank of long-run matrix 2 beta is identified AIC -35.2253 HQ -34.3344

no. of parameters 85 no. long-run restrictions 5

SC FPE

-33.0245 1.08703e-015

LR test of restrictions: Chi"2(5) = 3.6020 [0.6080]

Figure A6. Output from testing restrictions on a and 3 using 'General restrictions' in PcGive 10.1.

APPENDIX 267

inception (although there is an 1(2) version available as a free download for users of the standard 7(1) version of Cats). Microfit 4.010 offers a modelling strategy based closely on the approach used in, for example, Garratt, Lee, Pesaran and Shin (1999), whereby the user moves toward estimating the con- ditional 7(1) model with exogenous variables. All three packages have their strengths and limitations (in comparison with each other), and therefore it is likely that different users will have different views on which they prefer.

10 Microfit 4.0, An Interactive Econometric Analysis, developed by Hashem Pesaran and Bahram Pesaran and distributed by Oxford University Press.

  • Applied Time Series Modelling and Forecasting
  • Contents
  • Preface
  • 1 Introduction and Overview
    • Some Initial Concepts
      • Data-generating Processes
      • Role of the Error Term ut and Statistical Inference
    • Forecasting
    • Outline of the Book
  • 2 Short- and Long-run Models
    • Long-run Models
    • Stationary and Non-stationary Time Series
    • Spurious Regressions
    • Cointegration
    • Short-run Models
    • Conclusion
  • 3 Testing for Unit Roots
    • The Dickey Fuller Test
      • Perron's Procedure
    • Augmented Dickey-Fuller Test
    • Power and Level of Unit Root Tests
    • Structural Breaks and Unit Root Test
    • Seasonal Unit Roots
    • Structural Breaks and Seasonal Unit Root Tests
    • Periodic Integration and Unit Root-testing
    • Conclusion on Unit Root Tests
  • 4 Cointegration in Single Equations
    • The Engle–Granger (EG) Approach
    • Testing for Cointegration with a Structural Break
    • Alternative Approaches
      • Dynamic Models
      • Fully Modified Estimators
    • Problems with the Single Equation Approach
    • Estimating the Short-run Dynamic Model
    • Seasonal Cointegration
    • Periodic Cointegration
    • Asymmetric Tests for Cointegration
    • Conclusions
  • 5 Cointegration in Multivariate Systems
    • The Johansen Approach
    • Testing the Order of Integration of the Variables
    • Formulation of the Dynamic Model
    • Testing for Reduced Rank
    • Deterministic Components in the Multivariate Model
    • Testing of Weak Exogeneity and VECM with Exogenous I(1) Variables
    • Testing for Linear Hypotheses on Cointegration Relations
    • Testing for Unique Cointegration Vectors
    • Joint Tests of Restrictions on alpha and beta
    • Seasonal Unit Roots
    • Seasonal Cointegration
    • Conclusions
    • Appendix 1 Programming in SHAZAM
  • 6 Modelling the Short-run Multivariate System
    • Introduction
    • Estimating the Long-run Cointegration Relationships
    • Parsimonious VECM
    • Conditional PVECM
    • Structural Modelling
    • Structural Macroeconomic Modelling
  • 7 Panel Data Models and Cointegration
    • Introduction
    • Panel Data and Modelling Techniques
    • Panel Unit Root Tests
    • Testing for Cointegration in Panels
    • Estimating Panel Cointegration Models
    • Conclusion on Testing for Unit Roots and Cointegration in Panel Data

FMBF computer lab3.pdf

FMBF: Computer Practical 3

Introduction

This workshop covers ARCH and GARCH models. You will see how to estimate the

various models and perform appropriate diagnostic testing to assist in choosing a

preferred model.

We will initially work with a dataset comprising exchange rate data for the period 2

January 1980 to 21 May 1987. The contents of this dataset are listed in Table 1.

Table 1: Data contained in GARCH.XLS

DAY Day of week (1 is Monday)

BP US$ - British Pound

CD US$ - Canadian Dollar

DM US$ - Deutsche Mark

JY US$ - Japanese Yen

SF US$ - Swiss Franc

Exercise 1: Volatility in daily exchange rates - ARCH Models

1. Download the data from duo and load into PcGive.

2. dlog all of the exchange rate series, multiplying by 100 so we have daily

percentage changes in each exchange rate, i.e for the DM it would be 100 * ln(DM)

- ln(DMt-1).

3. Plot the daily change data in PcGive; what conclusions do you come to?

4. Identify an appropriate AR model for each of the exchange rate series.

Hint: You will want to use ACF/PACF to help you here, as well as employing

‘overfitting’ to check the specification. You may find that there is no evidence of

serial correlation and thus changes in the exchange rate do not have persistence

and can be regarded as a random walk.

5. Test for ARCH effects by going to Test > Test... and selecting ARCH test with

order 1. At a minimum you should test an order of 1 and 6. Are ARCH effects

present (The null hypothesis is that there is no ARCH effect)?

Notes: you may save, square and plot the residuals (Test > Test Menu: Store in

Database… > Residuals, and use Calculator to calculate the squared error

terms), and then you can examine the ACF and PACF of these squared residuals.

6. Estimate an appropriate ARCH model based on your results from the previous

step (Model > Category: Models for financial data; Model class: GARCH

Models using PcGive > Formulate).

7. Select the variables from your AR model and click OK. In the Model Settings

dialogue box select the appropriate specification; for example, an ARCH(6) model

will be p=0 and q=6. Click OK and estimate using maximum likelihood.

8. Analyse the results from your model. In particular, you will want to check if any

of the parameters are insignificant, and if so consider a more parsimonious

specification. It may be that you want to perform a Wald test if you have more

than one insignificant parameter (Test > Test Menu: Exclusion Restrictions).

Notes: Review Brooks textbook on Page 234. The null hypothesis of Wald test is

α = 0. The example shows the results are significant, which means we reject the

null hypothesis that α1 = 0, and we do not exclude α1.

9. Perform further tests on your model from Test > Test.... Recall the Portmanteau is

the Ljung Box test. Can you improve the model?

Notes: You may wish to overfit by adding an extra AR and ARCH parameter.

Ljung Box test: Brooks textbook on Page 234-235.

We will now see if it is advantageous to formulate a more parsimonious GARCH(1,1)

model and examine different the types of GARCH models that we can estimate with

PcGive.

Notes: Brooks textbook on Page 232-444.

Exercice 2: Volatility in daily exchange rates - GARCH Models

1. Using the same AR specification identified above, go to the Model Settings

dialogue box, but this time specify p=1 and q=1 so we have a GARCH(1,1) model

(q/β captures lags of squared error terms, and p/α captures lags of conditional

variance).

2. Interpret the results. Consider if you can improve the model with a change in the

AR structure. As above, check the diagnostics.

Notes: GARCH(1,1) shows effect of lagged shocks dies out very slowly.

α+β=0.978, so the estimated process is close to being nonstationary. You may also

try a GARCH (2,1) model, although GARCH(2,2) will be too far.

3. Estimate an EGARCH(1,1) model using the AR specification you identified above.

To do this you will need to check the EGARCH box in Model Settings.

Notes: EGARCH model:

The coefficient of eps[-1] is γ. If γ<0, positive shocks generate less volatility than

negative shocks (bad news).

Brooks textbook on Page 406.

4. Estimate a GJR-GARCH(1,1) model (this type of GARCH specification.is from

Glosten et al. (1993). To do this, open Model Settings and expand the GARCH

variations section. Select Threshold GARCH. Brook Page 404.

5. Estimate a GARCH(1,1)-in-Mean. To do this, open Model Settings and expand

the GARCH variations section. Select h_t in mean. Brooks Page 409.

Notes: If h_t is positive and significant, it means higher risk given higher conditional

variance, yields higher expected returns.

For all of the above, you should carefully evaluate the adequacy of your model

with particular reference to the diagnostic tests.

We will now use our GARCH models to produce forecasts:

Exercice 3: Forecasting

1. Using your preferred AR(p)-GARCH(1,1) model, in the Estimate Model dialogue

box hold back a number of observations with the Less forecasts setting. Initially,

you may wish to try 14.

2. After estimating the model, go to Test > Forecast.... Select the number of forecasts

you would like. If you look under Options you are able to control the number of

pre-forecast observations that are graphed and there is also a check box for Write

results instead of graphing if you desire a print-out of the forecasts rather than a

graph.

3. Examine the forecasts from your model. Note that you can use Test > Store in

Database to commit the Forecasts and Forecasts standard errors to the database.

Notes: The conditional variance is increasing and is converging to the unconditional

variance. Several useful measures concerning the forecast errors are displayed,

including mean(Error), SD(Error), RMSE and MAPE. RMSE is root mean squared

error, and MAPE is mean absolute percent error. The smaller these errors are, the

better for the forecasting, which means the model forecasts are able to account for

much of the variability of the out-of-sample part of the data.

The procedure for forecasting with ARMA models is similar to the above (Brooks

Page 257-258):

Exercice 4: Forecasting with ARMA models

1. Estimate an appropriate ARMA model, holding observations back for forecasting.

2. Use Test > Forecast... to produce a forecast from your model.

3. If you employ Write results instead of graphing you will see that PcGive displays

the mean(Error) (Heteroscedasticity-ajusted mean square error). This is the loss

function used by Bollerslev & Ghysels (1996) for model comparison. You will also

see RMSE (root mean square error) and MAPE (mean absolute error).

4. Evaluate the forecasting ability of your model. You may wish to compare it with

another suitable specification.

Points to note

 More details about PcGive's implementation of volatility models, together with a

tutorial, may be found in Hendry and Doornik (2001).

 It is often useful to use Model > Progress… to produce a summary table that can

aid analysis of competing models.

References

L. Glosten, R. Jagannathan, and D. Runkle. On the relation between the expected

value and the volatility of the nominal excess return on stocks. Journal of Finance,

48(5):1779{1801, 1993.

D. F. Hendry and J. A. Doornik. Empirical Econometric Modelling Using PcGive,

volume 1. Timberlake Consultants Ltd., 3 edition, 2001.

M. Verbeek. A Guide to Modern Econometrics. John Wiley & Sons, Inc., 2004.

FMBF computer lab4.pdf

Practice for FMBF computer LAB session 4

In this session, you are aiming to review the contents in the last three sessions we had through practicing the questions below with Givewin and PcGive.

Key words: AR, MA, ARMA, ARIMA Modelling; Cointegration; Volatility models: ARCH, GARCH, EGARCH, etc.. and forecasts

AR Modelling (Dataset: BA)

1. Can Graphics Function suggest a preferred model for the price of British Airways?

2. Constructing the model for price of BA.

3. Process the diagnostic steps to test the fitness of the model built up in question 2.

Unit root test (Dataset: FTSE)

4. Manual unit root test on the variable FTSE100 and explain the result.

5. Automated unit root testing on FTSE100 and explain the result.

6. If appropriate, test for the presence of I(2) for FTSE100 series.

Cointegration-EG test (Dataset: FTSE)

7. Does cointegration exist between FTSE100 and FTSEALL?

Cointegration-Johansen test (Dataset: Johansen)

8. Detect cointegration and find out the relationship among Yb Yc Yd.

ARCH and GARCH modelling (Dataset: GARCH)

9. Build up a proper model for the series of exchange rate of Canadian Dollar (variable CD in the dataset) and explain why the model you obtain should be a preferred model.

10. Use your preferred model to produce forecasts.

additional topic.pdf

LIMITED DEPENDENT VARIABLE

MODELS

(Additional topic)

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008 1

Some Examples of when Limited Dependent Variables may

be used

• There are numerous examples of instances where this may arise, for example where we want to model:

• Why firms choose to list their shares on the NASDAQ rather than the NYSE

• Why some stocks pay dividends while others do not

• What factors affect whether countries default on their sovereign debt

• Why some firms choose to issue new stock to finance an expansion while others issue bonds

• Why some firms choose to engage in stock splits while others do not.

• It is fairly easy to see in all these cases that the appropriate form for the dependent variable would be a 0-1 dummy variable since there are only two possible outcomes. There are, of course, also situations where it would be more useful to allow the dependent variable to take on other values, but these will be considered later.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

The Linear Probability Model

• We will first examine a simple and obvious, but unfortunately flawed, method for dealing with binary dependent variables, known as the linear probability model.

• it is based on an assumption that the probability of an event occurring, Pi, is linearly related to a set of explanatory variables

• The actual probabilities cannot be observed, so we would estimate a model where the outcomes, yi (the series of zeros and ones), would be the dependent variable.

• This is then a linear regression model and would be estimated by OLS.

• The set of explanatory variables could include either quantitative variables or dummies or both.

• The fitted values from this regression are the estimated probabilities for yi =1 for each observation i.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

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The Linear Probability Model

• The slope estimates for the linear probability model can be interpreted as the change in the probability that the dependent variable will equal 1 for a one- unit change in a given explanatory variable, holding the effect of all other explanatory variables fixed.

• Suppose, for example, that we wanted to model the probability that a firm i will pay a dividend p(yi = 1) as a function of its market capitalisation (x2i, measured in millions of US dollars), and we fit the following line:

where denotes the fitted or estimated probability for firm i.

• This model suggests that for every $1m increase in size, the probability that the firm will pay a dividend increases by 0.012 (or 1.2%).

• A firm whose stock is valued at $50m will have a -0.3+0.01250=0.3 (or 30%) probability of making a dividend payment.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

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The Fatal Flaw of the Linear Probability Model

• Graphically, the situation we have is

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Disadvantages of the Linear Probability Model

• While the linear probability model is simple to estimate and intuitive to interpret, the diagram on the previous slide should immediately signal a problem with this setup.

• For any firm whose value is less than $25m, the model-predicted probability of dividend payment is negative, while for any firm worth more than $88m, the probability is greater than one.

• Clearly, such predictions cannot be allowed to stand, since the probabilities should lie within the range (0,1).

• An obvious solution is to truncate the probabilities at 0 or 1, so that a probability of -0.3, say, would be set to zero, and a probability of, say, 1.2, would be set to 1.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Disadvantages of the Linear Probability Model 2

• However, there are at least two reasons why this is still not adequate.

• The process of truncation will result in too many observations for which the estimated probabilities are exactly zero or one.

• More importantly, it is simply not plausible to suggest that the firm's probability of paying a dividend is either exactly zero or exactly one. Are we really certain that very small firms will definitely never pay a dividend and that large firms will always make a payout?

• Probably not, and so a different kind of model is usually used for binary dependent variables either a logit or a probit specification.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Disadvantages of the Linear Probability Model 3

• The LPM also suffers from a couple of more standard econometric problems that we have examined in previous chapters.

• Since the dependent variable only takes one or two values, for given (fixed in repeated samples) values of the explanatory variables, the disturbance term will also only take on one of two values.

• Hence the error term cannot plausibly be assumed to be normally distributed.

• Since the disturbance term changes systematically with the explanatory variables, the former will also be heteroscedastic.

• It is therefore essential that heteroscedasticity-robust standard errors are always used in the context of limited dependent variable models.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Logit and Probit: Better Approaches

• Both the logit and probit model approaches are able to overcome the limitation of the LPM that it can produce estimated probabilities that are negative or greater than one.

• They do this by using a function that effectively transforms the regression model so that the fitted values are bounded within the (0,1) interval.

• Visually, the fitted regression model will appear as an S-shape rather than a straight line, as was the case for the LPM.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

The Logit Model

• The logit model is so-called because it uses a the cumulative logistic distribution to transform the model so that the probabilities follow the S- shape given on the previous slide.

• With the logistic model, 0 and 1 are asymptotes to the function and thus the probabilities will never actually fall to exactly zero or rise to one, although they may come infinitesimally close.

• The logit model is not linear (and cannot be made linear by a transformation) and thus is not estimable using OLS.

• Instead, maximum likelihood is usually used to estimate the parameters of the model.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Using a Logit to Test the Pecking Order Hypothesis

• The theory of firm financing suggests that corporations should use the cheapest methods of financing their activities first (i.e. the sources of funds that require payment of the lowest rates of return to investors) and then only switch to more expensive methods when the cheaper sources have been exhausted.

• This is known as the “pecking order hypothesis”.

• Differences in the relative cost of the various sources of funds are argued to arise largely from information asymmetries since the firm's senior managers will know the true riskiness of the business, whereas potential outside investors will not.

• Hence, all else equal, firms will prefer internal finance and then, if further (external) funding is necessary, the firm's riskiness will determine the type of funding sought.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Data

• Helwege and Liang (1996) examine the pecking order hypothesis in the context of a set of US firms that had been newly listed on the stock market in 1983, with their additional funding decisions being tracked over the 1984 - 1992 period.

• Such newly listed firms are argued to experience higher rates of growth, and are more likely to require additional external funding than firms which have been stock market listed for many years.

• They are also more likely to exhibit information asymmetries due to their lack of a track record.

• The list of initial public offerings (IPOs) was obtained from the Securities Data Corporation and the Securities and Exchange Commission with data obtained from Compustat.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Aims of the Study and the Model

• A core objective of the paper is to determine the factors that affect the probability of raising external financing.

• As such, the dependent variable will be binary -- that is, a column of 1's (firm raises funds externally) and 0's (firm does not raise any external funds).

• Thus OLS would not be appropriate and hence a logit model is used.

• The explanatory variables are a set that aims to capture the relative degree of information asymmetry and degree of riskiness of the firm.

• If the pecking order hypothesis is supported by the data, then firms should be more likely to raise external funding the less internal cash they hold.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Variables used in the Model

• The variable deficit measures (capital expenditures + acquisitions + dividends - earnings).

• Positive deficit is a variable identical to deficit but with any negative deficits (i.e. surpluses) set to zero

• Surplus is equal to the negative of deficit for firms where deficit is negative

• Positive deficit  operating income is an interaction term where the two variables are multiplied together to capture cases where firms have strong investment opportunities but limited access to internal funds

• Assets is used as a measure of firm size

• Industry asset growth is the average rate of growth of assets in that firm's industry over the 1983-1992 period

• Firm's growth of sales is the growth rate of sales averaged over the previous 5 years

• Previous financing is a dummy variable equal to one for firms that obtained external financing in the previous year.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Results from Logit Estimation

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Source: Helwege and Liang (1996)

Analysis of Results

• The key variable, deficit has a parameter that is not statistically significant and hence the probability of obtaining external financing does not depend on the size of a firm's cash deficit.

• Or an alternative explanation, as with a similar result in the context of a standard regression model, is that the probability varies widely across firms with the size of the cash deficit so that the standard errors are large relative to the point estimate.

• The parameter on the surplus variable has the correct negative sign, indicating that the larger a firm's surplus, the less likely it is to seek external financing, which provides some limited support for the pecking order hypothesis.

• Larger firms (with larger total assets) are more likely to use the capital markets, as are firms that have already obtained external financing during the previous year.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

The Probit Model

• Instead of using the cumulative logistic function to transform the model, the cumulative normal distribution is sometimes used instead.

• This gives rise to the probit model.

• As for the logistic approach, this function provides a transformation to ensure that the fitted probabilities will lie between zero and one.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Logit or Probit?

• For the majority of the applications, the logit and probit models will give very similar characterisations of the data because the densities are very similar.

• That is, the fitted regression plots will be virtually indistinguishable, and the implied relationships between the explanatory variables and the probability that yi =1 will also be very similar.

• Both approaches are much preferred to the linear probability model. The only instance where the models may give non-negligibility different results occurs when the split of the yi between 0 and 1 is very unbalanced - for example, when yi =1 occurs only 10% of the time.

• Stock and Watson (2006) suggest that the logistic approach was traditionally preferred since the function does not require the evaluation of an integral and thus the model parameters could be estimated faster.

• However, this argument is no longer relevant given the computational speeds now achievable and the choice of one specification rather than the other is now usually arbitrary.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Parameter Interpretation for Logit and Probit Models

• Standard errors and t-ratios will automatically be calculated by the econometric software package used, and hypothesis tests can be conducted in the usual fashion.

• However, interpretation of the coefficients needs slight care.

• It is tempting, but incorrect, to state that a 1-unit increase in x2i, for example, causes a 2 % increase in the probability that the outcome corresponding to yi =1 will be realised.

• This would have been the correct interpretation for the linear probability model.

• However, for logit or probit models, this interpretation would be incorrect because the form of the function is Pi = 1 + 2 x2i + ui, for example, but rather Pi = F(x2i) where F represents the (non-linear) logistic or cumulative normal function.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Parameter Interpretation for Logit and Probit Models

• To obtain the required relationship between changes in x2i and Pi, we would need to differentiate F with respect to x2i and it turns out that this derivative is 2F(x2i) .

• So in fact, a 1-unit increase in x2i will cause a 2F(x2i) increase in probability.

• Usually, these impacts of incremental changes in an explanatory variable are evaluated by setting each of them to their mean values.

• These estimates are sometimes known as the marginal effects.

• There is also another way of interpreting discrete choice models known as the random utility model.

• The idea is that we can view the value of y that is chosen by individual i (either 0 or 1) as giving that person a particular level of utility, and the choice that is made will obviously be the one that generates the highest level of utility.

• This interpretation is particularly useful in the situation where the person faces a choice between more than 2 possibilities – see a later slide.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Goodness of Fit for Probit and Logit Models

• While it would be possible to calculate the values of the standard goodness of fit measures such as RSS, R2 these cease to have any real meaning.

• R2, if calculated in the usual fashion, will be misleading because the fitted values from the model can take on any value but the actual values will only be either 0 and 1.

• Thus if yi =1 and = 0.8, the model has effectively made the correct prediction, whereas R2 and will not give it full credit for this.

• Two goodness of fit measures that are commonly reported for limited dependent variable models are

• The percentage of yi values correctly predicted

• A measure known as „pseudo-R2‟ (also known as McFadden's R2), defined as one minus the ratio of the LLF for the logit or probit model to the LLF for a model with only an intercept.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

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Multinomial Linear Dependent Variables

• There are many instances where investors or financial agents are faced with more alternatives than a simple binary choice.

• For example:

• A company may be considering listing on the NYSE, the NASDAQ or the AMEX markets.

• A firm that is intending to take over another may choose to pay by cash, with shares, or with a mixture of both.

• A retail investor may be choosing between 5 different mutual funds.

• A credit ratings agency could assign 1 of 16 (AAA to B3/B-) different ratings classifications to a firm's debt.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Multinomial Linear Dependent Variables (Cont’d)

• Notice that the first three of these examples are different from the last one.

• In the first three cases, there is no natural ordering of the alternatives: the choice is simply made between them.

• In the final case, there is an obvious ordering, because a score of 1, denoting a AAA-rated bond, is better than a score of 2, denoting a AA1/AA+-rated bond, and so on.

• These two situations need to be distinguished and a different approach used in each case. In the first (when there is no natural ordering), a multinomial logit or probit would be used, while in the second (where there is an ordering), an ordered logit or probit would be used.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Discrete Choice Problems

• When the alternatives are unordered, this is sometimes called a discrete choice or multiple choice problem.

• The models used are derived from the principles of utility maximisation - that is, the agent chooses the alternative that maximises his utility relative to the others.

• Econometrically, this is captured using a simple generalisation of the binary setup discussed earlier. Thus the multinomial logit and probit are direct extensions of their binary counterparts.

• When there were only 2 choices (0, 1), we required just one equation to capture the

• probability that one or the other would be chosen.

• If there are now three alternatives, we would need two equations; for four alternatives, we would need three equations. In general, if there are m possible alternative choices, we need m-1 equations.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Modelling the Travel to Work Choice

• The multiple choice example most commonly used is that of the selection of the mode of transport for travel to work.

• Suppose that the journey may be made by car, bus, or bicycle (3 alternatives), and suppose that the explanatory variables are the person's income (I), total hours worked (H), their gender (G) and the distance travelled (D).

• We could set up 2 equations (e.g., for bus and car) and then travel by bicycle becomes a sort of reference point.

• While the fitted probabilities will always sum to unity by construction, as with the binomial case, there is no guarantee that they will all lie between zero and one.

• In order to make a prediction about which mode of transport a particular individual will use, given that the parameters in, the largest fitted probability would be set to one and the others set to zero.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Ordered Response Models

• Some limited dependent variables can be assigned numerical values that have a natural ordering.

• The most common example in finance is that of credit ratings, as discussed previously, but a further application is to modelling a security's bid-ask spread.

• In such cases, it would not be appropriate to use multinomial logit or probit since these techniques cannot take into account any ordering in the dependent variables.

• Using the credit rating example, the model is set up so that a particular bond falls in the AA+ category (using Standard and Poor's terminology) if its unobserved (latent) creditworthiness falls within a certain range that is too low to classify it as AAA and too high to classify it as AA.

• The boundary values between each rating are then estimated along with the model parameters.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Are Unsolicited Credit Ratings Biased Downwards?

• The main credit ratings agencies construct solicited ratings, which are those where the issuer of the debt contacts the agency and pays them a fee for producing the rating.

• Many firms globally do not seek a rating (because, for example, the firm believes that the ratings agencies are not well placed to evaluate the riskiness of debt in their country or because they do not plan to issue any debt or because they believe that they would be awarded a low rating).

• But the agency may produce a rating anyway. Such „unwarranted and unwelcome‟ ratings are known as unsolicited ratings.

• All of the major ratings agencies produce unsolicited ratings as well as solicited ones, and they argue that there is a market demand for this information even if the issuer would prefer not to be rated.

• Companies in receipt of unsolicited ratings argue that these are biased downwards relative to solicited ratings, and that they cannot be justified without the level of detail of information that can only be provided by the rated company itself.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Data and Methodology

• A study by Poon (2003) seeks to test the conjecture that unsolicited ratings are biased after controlling for the rated company's characteristics that pertain to its risk.

• The data employed comprise a pooled sample of all companies that appeared on the annual „issuer list‟ of S&P during the 1998-2000 years.

• This list contains both solicited and unsolicited ratings covering 295 firms over 15 countries and totaling 595 observations.

• As expected, the financial characteristics of the firms with unsolicited ratings are significantly weaker than those for firms that requested ratings.

• The core methodology employs an ordered probit model with explanatory variables comprising firm characteristics and a dummy variable for whether the firm's credit rating was solicited or not:

with

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

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where

• Ri are the observed ratings scores that are given numerical values as follows:

AA or above = 6, A = 5, BBB = 4, BB = 3, B = 2 and CCC or below = 1

• Ri * is the unobservable „true rating‟ (or „an unobserved continuous variable

representing S&P‟s assessment of the creditworthiness of issuer i‟)

• Xi is a vector of variables that explain the variation in ratings

•  is a vector of coefficients; i are the threshold parameters to be estimated

• i is a disturbance term that is assumed normally distributed.

• The explanatory variables attempt to capture the creditworthiness using publicly

available information.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Definitions of Variables

• Two specifications are estimated: the first includes the variables listed below, while the second additionally incorporates an interaction of the main financial variables with a dummy variable for whether the firm's rating was solicited (SOL) and separately with a dummy for whether the firm is based in Japan.

• The Japanese dummy is used since a disproportionate number of firms in the sample are from this country.

• The financial variables are ICOV - interest coverage (i.e. earnings \ interest); ROA - return on assets; DTC - total debt to capital; and SDTD - short term debt to total debt.

• Three variables SOVAA, SOVA, and SOVBBB are dummy variables that capture the debt issuer's sovereign credit rating (AA; A; BBB or below)

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Ordered Probit Results for the Determinants of Credit

Ratings

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Source: Poon (2003)

Analysis of Ordered Probit Results

• The key finding is that the SOL variable is positive and statistically significant in Model 1 (and it is positive but insignificant in Model 2).

• This indicates that even after accounting for the financial characteristics of the firms, unsolicited firms receive ratings on average 0.359 units lower than an otherwise identical firm that had requested a rating.

• The parameter estimate for the interaction term between the solicitation and Japanese dummies (SOL*JP) is positive and significant in both specifications, indicating strong evidence that Japanese firms soliciting ratings receive higher scores.

• On average, firms with stronger financial characteristics (higher interest coverage, higher return on assets, lower debt to total capital, or a lower ratio of short term debt to long term debt) have higher ratings.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

The Heckman 2-Step Procedure

• A major flaw that potentially exists within the above analysis is the self-selection bias or sample selection bias that may have arisen if firms that would have received lower credit ratings (because they have weak financials) elect not to solicit a rating.

• If the probit equation for the determinants of ratings is estimated ignoring this potential problem and it exists, the coefficients will be inconsistent.

• To get around this problem and to control for the sample selection bias, Heckman (1979) proposed a 2-step procedure.

• In this case would involve first estimating a 0-1 probit model for whether the firm chooses to solicit a rating and second estimating the ordered probit model for the determinants of the rating. The first stage probit model is

• where Yi = 1 if the firm has solicited a rating and 0 otherwise, and Yi * denotes the

latent propensity of issuer i to solicit a rating, Zi are the variables that explain the choice to be rated or not, and  are the parameters to be estimated.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

iii ZY  *

The Heckman 2-Step Procedure

• When this equation has been estimated, the rating Ri as defined above in will only be observed if Yi = 1.

• The error terms from the two equations, i and i follow a bivariate standard normal distribution with correlation  .

• The table on the following page shows the results from the two-step estimation procedure, with the estimates from the binary probit model for the decision concerning whether to solicit a rating in panel A and the determinants of ratings for rated firms in panel B.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

The Heckman 2-Step Procedure: Results

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Source: Poon (2003)

The Heckman 2-Step Procedure: Analysis

• A positive parameter value in panel A indicates that higher values of the associated variable increases the probability that a firm will elect to be rated.

• Of the four financial variables, only the return on assets and the short term debt as a proportion of total debt have correctly signed and significant (positive and negative respectively) impacts on the decision to be rated.

• The parameters on the sovereign credit rating dummy variables (SOVAA, SOVA and SOVB) are all significant and negative in sign, indicating that any debt issuer in a country with a high sovereign rating is less likely to solicit its own rating from S&P, other things equal.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

The Heckman 2-Step Procedure: Analysis (Cont’d)

• These sovereign rating dummy variables have the opposite sign in the ratings determinant equation (panel B) as expected, so that firms in countries where government debt is highly rated are themselves more likely to receive a higher rating.

• Of the four financial variables, only ROA has a significant (and positive) effect on the rating awarded.

• The dummy for Japanese firms is also positive and significant, and so are three of the four financial variables when interacted with the Japan dummy, indicating that S&P appears to attach different weights to the financial variables when assigning ratings to Japanese firms compared with comparable firms in other countries.

• Finally, the estimated correlation between the error terms in the decision to be rated equation and the ratings determinant equation, , is significant and negative (-0.836), indicating that the results in table 11.3 above would have been subject to self-selection bias and hence the results of the two-stage model are to be preferred.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Censored and Truncated Variables

• Censored or truncated variables occur when the range of values observable for the dependent variables is limited for some reason.

• Unlike the types of limited dependent variables examined so far, censored or truncated variables may not necessarily be dummies.

• A standard example is that of charitable donations by individuals.

• It is likely that some people would actually prefer to make negative donations (that is, to receive from the charity rather than to donate it), but since this is not possible, there will be many observations at exactly zero.

• So suppose, for example that we wished to model the relationship between donations to charity and peoples' annual incomes, in pounds.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Censored and Truncated Variables (Cont’d)

• Given the observed data, with many observations on the dependent variable stuck at zero, OLS would yield biased and inconsistent parameter estimates.

• An obvious, but flawed, way to get around this would be just to remove all of the zero observations altogether, since we do not know whether they should be truly zero or negative.

• However, as well as being inefficient (since information would be discarded), this would still yield biased and inconsistent estimates.

• This arises because the error term in such a regression would not have an expected value of zero, and it would also be correlated with the explanatory variable(s).

• For both censored and truncated data, OLS will not be appropriate, and an approach based on maximum likelihood must be used, although the model in each case would be slightly different.

• We can work out the marginal effects given the estimated parameters, but these are now more complex than in the logit or probit cases.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

The Differences between Censored and Truncated Variables

• When the terms are used in econometrics, censored and truncated data are different

• Censored data occur when the dependent variable has been „censored‟ at certain point so that values above (or below) this cannot be observed.

• Even though the dependent variable is censored, the corresponding values of the independent variables are still observable.

• As an example, suppose that a privatisation IPO is heavily oversubscribed, and you were trying to model the demand for the shares using household income, age, education, and region of residence as explanatory variables. The number of shares allocated to each investor may have been capped at, say 250, resulting in a truncated distribution.

• In this example, even though we are likely to have many share allocations at 250 and none above this figure, all of the observations on the independent variables are present and hence the dependent variable is censored, not truncated.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Truncated Variables

• A truncated dependent variable, on the other hand, occurs when the observations for both the dependent and the independent variables are missing when the dependent variable is above (or below) a certain threshold.

• Thus the key difference from censored data is that we cannot observe the xIs either, and so some observations are completely cut out or „truncated‟ from the sample.

• For example, suppose that a bank were interested in determining the factors (such as age, occupation and income) that affected a customer's decision as to whether to undertake a transaction in a branch or on-line. Suppose also that the bank tried to achieve this by encouraging clients to fill in an on-line questionnaire when they log on. There would be no data at all for those who opted to transact in person since they probably would not have even logged on to the bank's web-based system and so would not have the opportunity to complete the questionnaire.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Truncated Variables (Cont’d)

• Thus, dealing with truncated data is really a sample selection problem because the sample of data that can be observed is not representative of the population of interest - the sample is biased, very likely resulting in biased and inconsistent parameter estimates.

• This is a common problem, which will result whenever data for buyers or users only can be observed while data for non-buyers or non-users cannot.

• Of course, it is possible, although unlikely, that the population of interest is focused only on those who use the internet for banking transactions, in which case there would be no problem.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

The Tobit Model

• The approach usually used to estimate models with censored dependent variables is known as tobit analysis, named after Tobin (1958).

• To illustrate, suppose that we wanted to model the demand for privatisation IPO shares, as discussed above, as a function of income (x2i), age (x3i), education (x4i), and region of residence (x5i). The model would be

• yi * represents the true demand for shares (i.e. the number of shares requested)

and this will only be observable for demand less than 250.

• It is important to note in this model that 2, 3, etc., represent the impact on the number of shares demanded (of a unit change in x2i, x3i, etc.) and not the impact on the actual number of shares that will be bought (allocated).

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

250250

250

*

**

554433221

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

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

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Limitations of the Tobit Model

• Before moving on, two important limitations of tobit modelling should be noted.

• First, such models are much more seriously affected by non-normality and heteroscedasticity than are standard regression models, and biased and inconsistent estimation will result.

• Second, the tobit model requires it to be plausible that the dependent variable can have values close to the limit.

• There is no problem with the privatisation IPO example discussed above since the demand could be for 249 shares.

• However, it would not be appropriate to use the tobit model in situations where this is not the case, such as the number of shares issued by each firm in a particular month.

• For most companies, this figure will be exactly zero, but for those where it is not, the number will be much higher and thus it would not be feasible to issue, say, 1 or 3 or 15 shares.

• In this case, an alternative approach should be used.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Models for Truncated Dependent Variables

• For truncated data, a more general model is employed that contains two equations - one for whether a particular data point will fall into the observed or constrained categories and another for modelling the resulting variable.

• The second equation is equivalent to the tobit approach.

• This two-equation methodology allows for a different set of factors to affect the sample selection (for example the decision to set up internet access to a bank account) from the equation to be estimated (for example, to model the factors that affect whether a particular transaction will be conducted on-line or in a branch).

• If it is thought that the two sets of factors will be the same, then a single equation can be used and the tobit approach is sufficient.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Models for Truncated Dependent Variables (Cont’d)

• In many cases, however, the researcher may believe that the variables in the sample selection and estimation equations should be different.

• Thus the equations could be

where yi = yi * for ai

* > 0 and yi is unobserved for ai *  0.

• ai * denotes the relative „advantage‟ of being in the observed sample relative to

the unobserved sample.

• The first equation determines whether the particular data point i will be observed or not, by regressing a proxy for the latent (unobserved) variable, ai

*, on a set of factors, zi.

• The second equation is similar to the tobit model.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

ikikiiii

imimiiii

uxxxxy

zzzza





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

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Models for Truncated Dependent Variables (Cont’d)

• Ideally, the two equations will be fitted jointly by maximum likelihood.

• This is usually based on the assumption that the error terms, are multivariate normally distributed and allowing for any possible correlations between them.

• However, while joint estimation of the equations is more efficient, it is computationally more complex and hence a two-stage procedure popularised by Heckman (1976) is often used.

• The Heckman procedure allows for possible correlations between the error terms while estimating the equations separately in a clever way.

‘Introductory Econometrics for Finance’ ©

Chris Brooks 2008

Topic1.pdf

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 1

Topic 1

Univariate Time Series Models and

Their Application in Finance

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 2

• Where we attempt to predict returns using only information contained in their past values.

Some Notation and Concepts

• A Strictly Stationary Process

A strictly stationary process is one where

i.e. the probability measure for the sequence {yt} is the same as that for {yt+m}  m.

• A Weakly Stationary Process

If a series satisfies the next three equations, it is said to be weakly or covariance

stationary

1. E(yt) =  , t = 1,2,...,

2.

3.  t1 , t2

Univariate Time Series Models

P y b y b P y b y bt t n t m t m nn n { ,..., } { ,..., }

1 11 1     

E y yt t t t( )( ) 1 2 2 1      

E y yt t( )( )       2

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 3

• So if the process is covariance stationary, all the variances are the same and all the covariances depend on the difference between t1 and t2. The moments

, s = 0,1,2, ...

are known as the covariance function.

• The covariances, s, are known as autocovariances.

• However, the value of the autocovariances depend on the units of measurement of yt.

• It is thus more convenient to use the autocorrelations which are the autocovariances normalised by dividing by the variance:

, s = 0,1,2, ...

• If we plot s against s=0,1,2,... then we obtain the autocorrelation function or

correlogram.

Univariate Time Series Models (cont’d)

 

 s

s 0

E y E y y E yt t t s t s s( ( ))( ( ))    

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 4

• A white noise process is one with (virtually) no discernible structure. A definition of a white noise process is

• Thus the autocorrelation function will be zero apart from a single peak of 1 at s = 0. s  approximately N(0,1/T) where T = sample size

• We can use this to do significance tests for the autocorrelation coefficients by constructing a confidence interval.

• For example, a 95% confidence interval would be given by . If the sample autocorrelation coefficient, , falls outside this region for any value of s, then we reject the null hypothesis that the true value of the coefficient at lag s is zero.

A White Noise Process

E y

Var y

if t r otherwise

t

t

t r

( )

( )

 

 

 

2

2

0

 s T

1 96.1 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 5

• We can also test the joint hypothesis that all m of the k correlation coefficients are simultaneously equal to zero using the Q-statistic developed by Box and Pierce:

where T = sample size, m = maximum lag length

• The Q-statistic is asymptotically distributed as a .

• However, the Box Pierce test has poor small sample properties, so a variant

has been developed, called the Ljung-Box statistic:

• This statistic is very useful as a portmanteau (general) test of linear dependence in time series.

Joint Hypothesis Tests

m 2

 

 m

k

kTQ 1

2

  2

1

2

~2 m

m

k

k

kT TTQ 

  

 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 6

• Question:

Suppose that a researcher had estimated the first 5 autocorrelation coefficients using a series of length 100 observations, and found them to be (from 1 to 5): 0.207, -0.013, 0.086, 0.005, -0.022.

Test each of the individual coefficient for significance, and use both the Box- Pierce and Ljung-Box tests to establish whether they are jointly significant.

• Solution:

A coefficient would be significant if it lies outside (-0.196,+0.196) at the 5% level, so only the first autocorrelation coefficient is significant.

Q=5.09 and Q*=5.26

Compared with a tabulated 2(5)=11.1 at the 5% level, so the 5 coefficients are jointly insignificant.

An ACF Example

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 7

• Let ut (t=1,2,3,...) be a sequence of independently and identically

distributed (iid) random variables with E(ut)=0 and Var(ut)= , then

yt =  + ut + 1ut-1 + 2ut-2 + ... + qut-q

is a qth order moving average model MA(q).

• Its properties are

E(yt)=; Var(yt) = 0 = (1+ )2

Covariances

Moving Average Processes

 2

  1 2

2 2 2  ... q



  

 



qsfor

qsforsqqsss

s 0

,...,2,1)...( 2

2211  

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 8

1. Consider the following MA(2) process:

where ut is a zero mean white noise process with variance .

(i) Calculate the mean and variance of Xt

(ii) Derive the autocorrelation function for this process (i.e. express the

autocorrelations, 1, 2, ... as functions of the parameters 1 and

2).

(iii) If 1 = -0.5 and 2 = 0.25, sketch the acf of Xt.

Example of an MA Problem

2211   tttt uuuX  2

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 9

(i) If E(ut)=0, then E(ut-i)=0  i.

So

E(Xt) = E(ut + 1ut-1+ 2ut-2)= E(ut)+ 1E(ut-1)+ 2E(ut-2)=0

Var(Xt) = E[Xt-E(Xt)][Xt-E(Xt)]

but E(Xt) = 0, so

Var(Xt) = E[(Xt)(Xt)]

= E[(ut + 1ut-1+ 2ut-2)(ut + 1ut-1+ 2ut-2)]

= E[ +cross-products]

But E[cross-products]=0 since Cov(ut,ut-s)=0 for s0.

Solution

2

2

2

2

2

1

2

1

2

  ttt uuu 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 10

So Var(Xt) = 0= E [ ]

=

=

(ii) The acf of Xt.

1 = E[Xt-E(Xt)][Xt-1-E(Xt-1)]

= E[Xt][Xt-1]

= E[(ut +1ut-1+ 2ut-2)(ut-1 + 1ut-2+ 2ut-3)]

= E[( )]

=

=

Solution (cont’d)

2

2

2

2

2

1

2

1

2

  ttt uuu  22

2

22

1

2   22

2

2

1 )1(  

2

221

2

11   tt uu 

2

21

2

1   2

211 )(  

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 11

2 = E[Xt-E(Xt)][Xt-2-E(Xt-2)]

= E[Xt][Xt-2]

= E[(ut +1ut-1+2ut-2)(ut-2 +1ut-3+2ut-4)]

= E[( )]

=

3 = E[Xt-E(Xt)][Xt-3-E(Xt-3)]

= E[Xt][Xt-3]

= E[(ut +1ut-1+2ut-2)(ut-3 +1ut-4+2ut-5)]

= 0

So s = 0 for s > 2.

Solution (cont’d)

2

22 tu 2

2

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 12

Solution (cont’d)

We have the autocovariances, now calculate the autocorrelations:

(iii) For 1 = -0.5 and 2 = 0.25, substituting these into the formulae above gives 1 = -0.476, 2 = 0.190.

  0

0

0 1 

  3

3

0 0 

  s

s s   

0 0 2

)1(

)(

)1(

)(

2

2

2

1

211

22

2

2

1

2

211

0

1

1 







 



 



 

)1()1(

)(

2

2

2

1

2

22

2

2

1

2

2

0

2

2 





 

 

 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 13

Thus the acf plot will appear as follows:

ACF Plot

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

0 1 2 3 4 5 6

s

a c

f

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 14

• An autoregressive model of order p, an AR(p) can be expressed as

• Or using the lag operator notation:

Lyt = yt-1 Liyt = yt-i

• or

or where .

Autoregressive Processes

   ( ) ( ... )L L L Lp p   1 1 2

2

tptpttt uyyyy    ...2211

 

  p

i

titit uyy 1



 

 p

i

tt

i

it uyLy 1



tt uyL   )(

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 15

• The condition for stationarity of a general AR(p) model is that the

roots of all lie outside the unit circle.

• A stationary AR(p) model is required for it to have an MA()

representation.

• Example 1: Is yt = yt-1 + ut stationary?

The characteristic root is 1, so it is a unit root process (so non-

stationary)

• Example 2: Is yt = 3yt-1 - 0.25yt-2 + 0.75yt-3 +ut stationary?

The characteristic roots are 1, 2/3, and 2. Since only one of these lies

outside the unit circle, the process is non-stationary.

The Stationary Condition for an AR Model

1 01 2 2      z z zp

p...

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 16

• States that any stationary series can be decomposed into the sum of two

unrelated processes, a purely deterministic part and a purely stochastic

part, which will be an MA().

• For the AR(p) model, , ignoring the intercept, the Wold

decomposition is

where,

Wold’s Decomposition Theorem

   ( ) ( ... )L L L Lp p     1 1 2

2 1

tt uyL )(

tt uLy )(

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 17

• The moments of an autoregressive process are as follows. The mean is

given by

• The autocovariances and autocorrelation functions can be obtained by

solving what are known as the Yule-Walker equations:

• If the AR model is stationary, the autocorrelation function will decay

exponentially to zero.

The Moments of an Autoregressive Process

pppp

pp

pp















...

...

...

2211

22112

12111



E yt p

( ) ...

    

  1 1 2

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 18

• Consider the following simple AR(1) model

(i) Calculate the (unconditional) mean of yt.

For the remainder of the question, set =0 for simplicity.

(ii) Calculate the (unconditional) variance of yt.

(iii) Derive the autocorrelation function for yt.

Sample AR Problem

ttt uyy  11

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 19

(i) Unconditional mean:

E(yt) = E(+1yt-1)

= +1E(yt-1)

But also

E(yt-1)= E(+1yt-2)

So E(yt)=  +1 ( +1E(yt-2))

=  +1  +1 2

E(yt-2))

E(yt) =  +1  +1 2

E(yt-2))

=  +1  +1 2 ( +1E(yt-3))

=  +1  +1 2  +1

3 E(yt-3)

Solution

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 20

An infinite number of such substitutions would give

E(yt) =  (1+1+1 2

+...) + 1 y0

So long as the model is stationary, i.e. , then 1  = 0.

So E(yt) =  (1+1+1 2

+...) =

(ii) Calculating the variance of yt:

From Wold‟s decomposition theorem:

Solution (cont’d)

11 

ttt uyy  11

tt uLy  )1( 1

tt uLy 1

1 )1(  

tt uLLy ...)1( 22

11  

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 21

So long as , this will converge.

Var(yt) = E[yt-E(yt)][yt-E(yt)]

but E(yt) = 0, since we are setting  = 0.

Var(yt) = E[(yt)(yt)]

= E[ ]

= E[

= E[

=

=

=

Solution (cont’d)

11  ...2

2

111   tttt uuuy 

  .... 2

2

1112

2

111   tttttt uuuuuu 

)]...( 2

2

4

1

2

1

2

1

2 productscrossuuu ttt   

...)]( 2

2

4

1

2

1

2

1

2   ttt uuu 

...24

1

22

1

2  uuu 

...)1( 4

1

2

1

2   u

)1( 2

1

2

u

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 22

(iii) Turning now to calculating the acf, first calculate the autocovariances:

1 = Cov(yt, yt-1) = E[yt-E(yt)][yt-1-E(yt-1)]

Since a0 has been set to zero, E(yt) = 0 and E(yt-1) = 0, so

1 = E[ytyt-1]

1 = E[ ]

= E[

=

=

Solution (cont’d)

...)( 2

2

111   ttt uuu  ...)( 3

2

1211   ttt uuu 

]... 2

2

3

1

2

11 productscrossuu tt   

...25

1

23

1

2

1  

)1( 2

1

2

1



„Introductory Econometrics for Finance‟ © Chris Brooks 2002 23

Solution (cont’d)

For the second autocorrelation coefficient,

2 = Cov(yt, yt-2) = E[yt-E(yt)][yt-2-E(yt-2)]

Using the same rules as applied above for the lag 1 covariance

2 = E[ytyt-2]

= E[ ]

= E[

=

=

=

...)( 2

2

111   ttt uuu  ...)( 4

2

1312   ttt uuu 

]... 2

3

4

1

2

2

2

1 productscrossuu tt   

...24

1

22

1  

...)1( 4

1

2

1

22

1  

)1( 2

1

22

1



„Introductory Econometrics for Finance‟ © Chris Brooks 2002 24

Solution (cont’d)

• If these steps were repeated for 3, the following expression would be

obtained

3 =

and for any lag s, the autocovariance would be given by

s =

The acf can now be obtained by dividing the covariances by the

variance:

)1( 2

1

23

1



)1( 2

1

2

1



s

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 25

Solution (cont’d)

0 =

1 = 2 =

3 =

s =

1 0

0  

1

2

1

2

2

1

2

1

0

1

)1(

)1(



 

  

  

  

  

 2

1

2

1

2

2

1

22

1

0

2

)1(

)1(



 

  

  

  

  

3

1

s

1

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 26

• Measures the correlation between an observation k periods ago and the current observation, after controlling for observations at intermediate lags (i.e. all lags < k).

• So kk measures the correlation between yt and yt-k after removing the effects of yt-k+1 , yt-k+2 , …, yt-1 .

• At lag 1, the acf = pacf always

• At lag 2, 22 = (2-1 2) / (1-1

2)

• For lags 3+, the formulae are more complex.

The Partial Autocorrelation Function (denoted kk)

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 27

• The pacf is useful for telling the difference between an AR process and an

ARMA process.

• In the case of an AR(p), there are direct connections between yt and yt-s only

for s p.

• So for an AR(p), the theoretical pacf will be zero after lag p.

• In the case of an MA(q), this can be written as an AR(), so there are direct connections between yt and all its previous values.

• For an MA(q), the theoretical pacf will be geometrically declining.

The Partial Autocorrelation Function (denoted kk)

(cont’d)

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 28

• By combining the AR(p) and MA(q) models, we can obtain an ARMA(p,q)

model:

where

and

or

with

ARMA Processes

   ( ) ...L L L Lp p    1 1 2

2

q

qLLLL   ...1)( 2

21

tt uLyL )()(  

tqtqttptpttt uuuuyyyy    ...... 22112211

stuuEuEuE sttt  ,0)(;)(;0)( 22 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 29

• Similar to the stationarity condition, we typically require the MA(q) part of the model to have roots of (z)=0 greater than one in absolute value.

• The mean of an ARMA series is given by

• The autocorrelation function for an ARMA process will display combinations of behaviour derived from the AR and MA parts, but for lags beyond q, the acf will simply be identical to the individual AR(p) model.

The Invertibility Condition

E yt p

( ) ...

    

  1 1 2

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 30

An autoregressive process has

• a geometrically decaying acf

• number of spikes of pacf = AR order

A moving average process has

• Number of spikes of acf = MA order

• a geometrically decaying pacf

Summary of the Behaviour of the acf for

AR and MA Processes

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 31

The acf and pacf are not produced analytically from the relevant formulae for a model of that

type, but rather are estimated using 100,000 simulated observations with disturbances drawn

from a normal distribution.

ACF and PACF for an MA(1) Model: yt = – 0.5ut-1 + ut

Some sample acf and pacf plots

for standard processes

-0.45

-0.4

-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0

0.05

1 2 3 4 5 6 7 8 9 10

Lag

a c f

a n

d p

a c f

acf

pacf

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 32

ACF and PACF for an MA(2) Model:

yt = 0.5ut-1 - 0.25ut-2 + ut

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

1 2 3 4 5 6 7 8 9 10

Lags

a c f

a n

d p

a c f

acf

pacf

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 33

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1 2 3 4 5 6 7 8 9 10

Lags

a c f

a n

d p

a c f

acf

pacf

ACF and PACF for a slowly decaying AR(1) Model:

yt = 0.9yt-1 + ut

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 34

ACF and PACF for a more rapidly decaying AR(1)

Model: yt = 0.5yt-1 + ut

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

1 2 3 4 5 6 7 8 9 10

Lags

a c f

a n

d p

a c f

acf

pacf

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 35

ACF and PACF for a more rapidly decaying AR(1)

Model with Negative Coefficient: yt = -0.5yt-1 + ut

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

1 2 3 4 5 6 7 8 9 10

Lags

a c f

a n

d p

a c f

acf

pacf

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 36

ACF and PACF for a Non-stationary Model

(i.e. a unit coefficient): yt = yt-1 + ut

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1 2 3 4 5 6 7 8 9 10

Lags

a c f

a n

d p

a c f

acf

pacf

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 37

ACF and PACF for an ARMA(1,1):

yt = 0.5yt-1 + 0.5ut-1 + ut

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1 2 3 4 5 6 7 8 9 10

Lags

a c f

a n

d p

a c f

acf

pacf

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 38

• Box and Jenkins (1970) were the first to approach the task of estimating an ARMA model in a systematic manner. There are 3 steps to their approach:

1. Identification

2. Estimation

3. Model diagnostic checking

Step 1:

- Involves determining the order of the model.

- Use of graphical procedures

- A better procedure is now available

Building ARMA Models

- The Box Jenkins Approach

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 39

Step 2:

- Estimation of the parameters

- Can be done using least squares or maximum likelihood depending on the

model.

Step 3:

- Model checking

Box and Jenkins suggest 2 methods:

- deliberate overfitting

- residual diagnostics

Building ARMA Models

- The Box Jenkins Approach (cont’d)

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 40

• Identification would typically not be done using acf‟s.

• We want to form a parsimonious model.

• Reasons:

- variance of estimators is inversely proportional to the number of degrees of

freedom.

- models which are profligate might be inclined to fit to data specific features

• This gives motivation for using information criteria, which embody 2 factors

- a term which is a function of the RSS

- some penalty for adding extra parameters

• The object is to choose the number of parameters which minimises the information criterion.

Some More Recent Developments in

ARMA Modelling

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 41

• The information criteria vary according to how stiff the penalty term is.

• The three most popular criteria are Akaike‟s (1974) information criterion (AIC), Schwarz‟s (1978) Bayesian information criterion (SBIC), and the Hannan-Quinn criterion (HQIC).

where k = p + q + 1, T = sample size. So we min. IC s.t.

SBIC embodies a stiffer penalty term than AIC.

• Which IC should be preferred if they suggest different model orders?

– SBIC is strongly consistent but (inefficient).

– AIC is not consistent, and will typically pick “bigger” models.

Information Criteria for Model Selection

AIC k T ln(  ) / 2 2

p p q q ,

T T

k SBIC ln)ˆln( 2  

))ln(ln( 2

)ˆln( 2 T T

k HQIC  

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 42

• As distinct from ARMA models. The I stands for integrated.

• An integrated autoregressive process is one with a characteristic root

on the unit circle.

• Typically researchers difference the variable as necessary and then

build an ARMA model on those differenced variables.

• An ARMA(p,q) model in the variable differenced d times is equivalent

to an ARIMA(p,d,q) model on the original data.

ARIMA Models

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 43

• Another modelling and forecasting technique

• How much weight do we attach to previous observations?

• Expect recent observations to have the most power in helping to forecast future values of a series.

• The equation for the model

St =  yt + (1-)St-1 (1)

where

 is the smoothing constant, with 01

yt is the current realised value

St is the current smoothed value

Exponential Smoothing

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 44

• Lagging (1) by one period we can write

St-1 =  yt-1 + (1-)St-2 (2)

• and lagging again

St-2 =  yt-2 + (1-)St-3 (3)

• Substituting into (1) for St-1 from (2)

St =  yt + (1-)( yt-1 + (1-)St-2)

=  yt + (1-) yt-1 + (1-)2 St-2 (4)

• Substituting into (4) for St-2 from (3)

St =  yt + (1-) yt-1 + (1-)2 St-2

=  yt + (1-) yt-1 + (1-)2( yt-2 + (1-)St-3)

=  yt + (1-) yt-1 + (1-)2 yt-2 + (1-)3 St-3

Exponential Smoothing (cont’d)

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 45

• T successive substitutions of this kind would lead to

since 0, the effect of each observation declines exponentially as we

move another observation forward in time.

• Forecasts are generated by

ft+s = St

for all steps into the future s = 1, 2, ...

• This technique is called single (or simple) exponential smoothing.

Exponential Smoothing (cont’d)

    0

0

11 SyS T

T

i

it

i

t   

  

  

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 46

• It doesn‟t work well for financial data because

– there is little structure to smooth

– it cannot allow for seasonality

– it is an ARIMA(0,1,1) with MA coefficient (1-) - (See Granger & Newbold, p174)

– forecasts do not converge on long term mean as s

• Can modify single exponential smoothing

– to allow for trends (Holt‟s method)

– or to allow for seasonality (Winter‟s method).

• Advantages of Exponential Smoothing

– Very simple to use

– Easy to update the model if a new realisation becomes available.

Exponential Smoothing (cont’d)

Topic2.pdf

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 1

Topic 2

Multivariate models

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 2

Simultaneous Equations Models

• All the models we have looked at thus far have been single equations models of the form y = X + u

• All of the variables contained in the X matrix are assumed to be EXOGENOUS.

• y is an ENDOGENOUS variable.

An example from economics to illustrate - the demand and supply of a good:

(1)

(2)

(3)

where = quantity of the good demanded

= quantity of the good supplied

St = price of a substitute good

Tt = some variable embodying the state of technology

Q P S udt t t t     

Q P T vst t t t     

Q Qdt st

Qdt

Qst

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 3

• Assuming that the market always clears, and dropping the time subscripts for simplicity

(4)

(5)

This is a simultaneous STRUCTURAL FORM of the model.

• The point is that price and quantity are determined simultaneously (price affects quantity and quantity affects price).

• P and Q are endogenous variables, while S and T are exogenous.

• We can obtain REDUCED FORM equations corresponding to (4) and (5) by solving equations (4) and (5) for P and for Q (separately).

Simultaneous Equations Models:

The Structural Form

Q P S u     

Q P T v     

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 4

• Solving for Q,

(6)

• Solving for P,

(7)

• Rearranging (6),

(8)

Obtaining the Reduced Form

    P S u      P T v

Q S u Q T v

  

        

     P P T S v u      

( ) ( ) ( )           P T S v u

P T S v u

 

 

 

 

 

 

 

   

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 5

• Multiplying (7) through by ,

(9)

• (8) and (9) are the reduced form equations for P and Q.

Obtaining the Reduced Form (cont’d)

       Q S u Q T v      

       Q Q T S u v      

( ) ( ) ( )             Q T S u v

Q T S u v

 

 

 

 

 

 



 



 

 

 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 6

• But what would happen if we had estimated equations (4) and (5), i.e. the structural form equations, separately using OLS?

• Both equations depend on P. One of the CLRM assumptions was that E(Xu) = 0, where X is a matrix containing all the variables on the RHS of the equation.

• It is clear from (8) that P is related to the errors in (4) and (5) - i.e. it is stochastic.

• What would be the consequences for the OLS estimator, , if we ignore the simultaneity?

Simultaneous Equations Bias



„Introductory Econometrics for Finance‟ © Chris Brooks 2002 7

• Recall that and

• So that

• Taking expectations,

• If the X‟s are non-stochastic, E(Xu) = 0, which would be the case in a single equation system, so that , which is the condition for unbiasedness.

• But .... if the equation is part of a system, then E(Xu)  0, in general.

Simultaneous Equations Bias (cont’d)

 ( ' ) '  X X X y1 y X u 

E E E X X X u

X X E X u

( ) ( ) (( ' ) ' )

( ' ) ( ' )

 

 

 

1

1

E( ) 

uXXX

uXXXXXXX

uXXXX

')'(

')'(')'(

)(')'(ˆ

1

11

1





„Introductory Econometrics for Finance‟ © Chris Brooks 2002 8

• Conclusion: Application of OLS to structural equations which are part

of a simultaneous system will lead to biased coefficient estimates.

• Is the OLS estimator still consistent, even though it is biased?

• No - In fact the estimator is inconsistent as well.

• Hence it would not be possible to estimate equations (4) and (5)

validly using OLS.

Simultaneous Equations Bias (cont’d)

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 9

So What Can We Do?

• Taking equations (8) and (9), we can rewrite them as

(10)

(11)

• We CAN estimate equations (10) & (11) using OLS since all the RHS variables are exogenous.

• But ... we probably don‟t care what the values of the  coefficients are; what we wanted were the original parameters in the structural equations - , , , , , .

Avoiding Simultaneous Equations Bias

P T S      10 11 12 1

Q T S      20 21 22 2

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 10

Can We Retrieve the Original Coefficients from the ‟s?

Short answer: sometimes.

• As well as simultaneity, we sometimes encounter another problem: identification.

• Consider the following demand and supply equations

Supply equation (12)

Demand equation (13)

We cannot tell which is which!

• Both equations are UNIDENTIFIED or NOT IDENTIFIED, or UNDERIDENTIFIED.

• The problem is that we do not have enough information from the equations to estimate 4 parameters. Notice that we would not have had this problem with equations (4) and (5) since they have different exogenous variables.

Identification of Simultaneous Equations

Q P  

Q P  

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 11

• We could have three possible situations:

1. An equation is unidentified

· like (12) or (13)

· we cannot get the structural coefficients from the reduced form estimates

2. An equation is exactly identified

· e.g. (4) or (5)

· can get unique structural form coefficient estimates

3. An equation is over-identified

· Example given later

· More than one set of structural coefficients could be obtained from the reduced form.

What Determines whether an Equation is Identified

or not?

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 12

• How do we tell if an equation is identified or not?

• There are two conditions we could look at:

- The order condition - is a necessary but not sufficient condition for an

equation to be identified.

- The rank condition - is a necessary and sufficient condition for

identification. We specify the structural equations in a matrix form and

consider the rank of a coefficient matrix.

What Determines whether an Equation is Identified

or not? (cont’d)

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 13

Statement of the Order Condition (from Ramanathan 1995, pp.666)

• Let G denote the number of structural equations. An equation is just identified if the number of variables excluded from an equation is G-1.

• If more than G-1 are absent, it is over-identified. If less than G-1 are absent, it is not identified.

Example

• In the following system of equations, the Y‟s are endogenous, while the X‟s are exogenous. Determine whether each equation is over-, under-, or just- identified.

(14)-(16)

Simultaneous Equations Bias (cont’d)

Y Y Y X X u

Y Y X u

Y Y u

1 0 1 2 3 3 4 1 5 2 1

2 0 1 3 2 1 2

3 0 1 2 3

     

   

  

    

  

 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 14

Solution

G = 3;

If # excluded variables = 2, the eqn is just identified

If # excluded variables > 2, the eqn is over-identified

If # excluded variables < 2, the eqn is not identified

Equation 14: Not identified

Equation 15: Just identified

Equation 16: Over-identified

Simultaneous Equations Bias (cont’d)

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 15

• How do we tell whether variables really need to be treated as endogenous or not?

• Consider again equations (14)-(16). Equation (14) contains Y2 and Y3 - but do we really need equations for them?

• We can formally test this using a Hausman test, which is calculated as follows:

1. Obtain the reduced form equations corresponding to (14)-(16). The reduced forms turn out to be:

(17)-(19)

Estimate the reduced form equations (17)-(19) using OLS, and obtain the fitted values,

Tests for Exogeneity

Y X X v

Y X v

Y X v

1 10 11 1 12 2 1

2 20 21 1 2

3 30 31 1 3

   

  

  

  

 

 

 ,  , Y Y Y1 2 3

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 16

2. Run the regression corresponding to equation (14).

3. Run the regression (14) again, but now also including the fitted values

as additional regressors:

(20)

4. Use an F-test to test the joint restriction that 2 = 0, and 3 = 0. If the

null hypothesis is rejected, Y2 and Y3 should be treated as endogenous.

Tests for Exogeneity (cont’d)

 , Y Y2 3

1

1

33

1

222514332101 ˆˆ uYYXXYYY  

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 17

• Consider the following system of equations:

(21-23)

• Assume that the error terms are not correlated with each other. Can we estimate the equations individually using OLS?

• Equation 21: Contains no endogenous variables, so X1 and X2 are not correlated with u1. So we can use OLS on (21).

• Equation 22: Contains endogenous Y1 together with exogenous X1 and X2. We can use OLS on (22) if all the RHS variables in (22) are uncorrelated with that equation‟s error term. In fact, Y1 is not correlated with u2 because there is no Y2 term in equation (21). So we can use OLS on (22).

Recursive Systems

Y X X u

Y Y X X u

Y Y Y X X u

1 10 11 1 12 2 1

2 20 21 1 21 1 22 2 2

3 30 31 1 32 2 31 1 32 2 3

   

    

     

  

   

    

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 18

• Equation 23: Contains both Y1 and Y2; we require these to be

uncorrelated with u3. By similar arguments to the above, equations

(21) and (22) do not contain Y3, so we can use OLS on (23).

• This is known as a RECURSIVE or TRIANGULAR system. We do

not have a simultaneity problem here.

• But in practice not many systems of equations will be recursive...

Recursive Systems (cont’d)

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 19

• Cannot use OLS on structural equations, but we can validly apply it to

the reduced form equations.

• If the system is just identified, ILS involves estimating the reduced

form equations using OLS, and then using them to substitute back to

obtain the structural parameters.

• However, ILS is not used much because

1. Solving back to get the structural parameters can be tedious.

2. Most simultaneous equations systems are over-identified.

Indirect Least Squares (ILS)

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 20

• In fact, we can use this technique for just-identified and over-identified

systems.

• Two stage least squares (2SLS or TSLS) is done in two stages:

Stage 1:

• Obtain and estimate the reduced form equations using OLS. Save the

fitted values for the dependent variables.

Stage 2:

• Estimate the structural equations, but replace any RHS endogenous

variables with their stage 1 fitted values.

Estimation of Systems

Using Two-Stage Least Squares

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 21

Example: Say equations (14)-(16) are required.

Stage 1:

• Estimate the reduced form equations (17)-(19) individually by OLS and obtain the fitted values, .

Stage 2:

• Replace the RHS endogenous variables with their stage 1 estimated values:

(24)-(26)

• Now and will not be correlated with u1, will not be correlated with u2 , and will not be correlated with u3 .

Estimation of Systems

Using Two-Stage Least Squares (cont’d)

 ,  , Y Y Y1 2 3

Y Y Y X X u

Y Y X u

Y Y u

1 0 1 2 3 3 4 1 5 2 1

2 0 1 3 2 1 2

3 0 1 2 3

     

   

  

    

  

 

 

Y2 Y3

Y3

Y2

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 22

• It is still of concern in the context of simultaneous systems whether the

CLRM assumptions are supported by the data.

• If the disturbances in the structural equations are autocorrelated, the

2SLS estimator is not even consistent.

• The standard error estimates also need to be modified compared with

their OLS counterparts, but once this has been done, we can use the

usual t- and F-tests to test hypotheses about the structural form

coefficients.

Estimation of Systems

Using Two-Stage Least Squares (cont’d)

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 23

• Recall that the reason we cannot use OLS directly on the structural

equations is that the endogenous variables are correlated with the errors.

• One solution to this would be not to use Y2 or Y3 , but rather to use some

other variables instead.

• We want these other variables to be (highly) correlated with Y2 and Y3, but

not correlated with the errors - they are called INSTRUMENTS.

• Say we found suitable instruments for Y2 and Y3, z2 and z3 respectively. We

do not use the instruments directly, but run regressions of the form

(27) & (28)

Instrumental Variables

Y z

Y z

2 1 2 2 1

3 3 4 3 2

  

  

  

  

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 24

• Obtain the fitted values from (27) & (28), and , and replace Y2 and

Y3 with these in the structural equation.

• We do not use the instruments directly in the structural equation.

• It is typical to use more than one instrument per endogenous variable.

• If the instruments are the variables in the reduced form equations, then

IV is equivalent to 2SLS.

Instrumental Variables (cont’d)

Y2 Y3

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 25

What Happens if We Use IV / 2SLS Unnecessarily?

• The coefficient estimates will still be consistent, but will be inefficient compared to those that just used OLS directly.

The Problem With IV

• What are the instruments?

Solution: 2SLS is easier.

Other Estimation Techniques

1. 3SLS - allows for non-zero covariances between the error terms.

2. LIML - estimating reduced form equations by maximum likelihood

3. FIML - estimating all the equations simultaneously using maximum

likelihood

Instrumental Variables (cont’d)

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 26

• George and Longstaff (1993)

• Introduction

- Is trading activity related to the size of the bid / ask spread?

- How do spreads vary across options?

• How Might the Option Price / Trading Volume and the Bid / Ask Spread be Related?

Consider 3 possibilities:

1. Market makers equalise spreads across options.

2. The spread might be a constant proportion of the option value.

3. Market makers might equalise marginal costs across options irrespective

of trading volume.

An Example of the Use of 2SLS: Modelling

the Bid-Ask Spread and Volume for Options

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 27

• The S&P 100 Index has been traded on the CBOE since 1983 on a

continuous open-outcry auction basis.

• Transactions take place at the highest bid or the lowest ask.

• Market making is highly competitive.

Market Making Costs

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 28

• For every contract (100 options) traded, a CBOE fee of 9c and an

Options Clearing Corporation (OCC) fee of 10c is levied on the firm

that clears the trade.

• Trading is not continuous.

• Average time between trades in 1989 was approximately 5 minutes.

What Are the Costs Associated with Market Making?

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 29

• The CBOE limits the tick size:

$1/8 for options worth $3 or more

$1/16 for options worth less than $3

• The spread is likely to depend on trading volume

... but also trading volume is likely to depend on the spread.

• So there will be a simultaneous relationship.

The Influence of Tick-Size Rules on Spreads

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 30

• All trading days during 1989 are used for observations.

• The average bid & ask prices are calculated for each option during the time 2:00pm – 2:15pm Central Standard time.

• The following are then dropped from the sample for that day:

1. Any options that do not have bid / ask quotes reported during the ¼ hour.

2. Any options with fewer than 10 trades during the day.

• The option price is defined as the average of the bid & the ask.

• We get a total of 2456 observations. This is a pooled regression.

The Data

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 31

• For the calls:

(1)

(2)

• And symmetrically for the puts:

(3)

(4)

where PRi & CRi are the squared deltas of the options

The Models

CBA CDUM C CL T CR ei i i i i i i           0 1 2 3 4 5

CL CBA T T M vi i i i i i         0 1 2 3 2

4 2

PBA PDUM P PL T PR ui i i i i i i           0 1 2 3 4 5

PL PBA T T M wi i i i i i         0 1 2 3 2

4 2

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 32

• CDUMi and PDUMi are dummy variables

= 0 if Ci or Pi < $3

= 1 if Ci or Pi  $3

• T2 allows for a nonlinear relationship between time to maturity and the

spread.

• M2 is used since ATM options have a higher trading volume.

• Aside: are the equations identified?

• Equations (1) & (2) and then separately (3) & (4) are estimated using

2SLS.

The Models (cont’d)

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 33

Results 1

Call Bid-Ask Spread and Trading Volume Regression

iiiiiii eCRTCLCCDUMCBA  543210  (6.55)

iiiiii vMTTCBACL  2

4

2

3210  (6.56)

0 1 2 3 4 5 Adj. R 2

0.08362

(16.80)

0.06114

(8.63)

0.01679

(15.49)

0.00902

(14.01)

-0.00228

(-12.31)

-0.15378

(-12.52)

0.688

0 1 2 3 4 Adj. R 2

-3.8542

(-10.50)

46.592

(30.49)

-0.12412

(-6.01)

0.00406

(14.43)

0.00866

(4.76)

0.618

Note: t-ratios in parentheses. Source: George and Longstaff (1993). Reprinted with the permission of

the School of Business Administration, University of Washington.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 34

Results 2

Put Bid-Ask Spread and Trading Volume Regression

iiiiiii uPRTPLPPDUMPBA  543210  (6.57)

iiiiii wMTTPBAPL  2

4

2

3210  (6.58)

0 1 2 3 4 5 Adj. R 2

0.05707

(15.19)

0.03258

(5.35)

0.01726

(15.90)

0.00839

(12.56)

-0.00120

(-7.13)

-0.08662

(-7.15)

0.675

0 1 2 3 4 Adj. R 2

-2.8932

(-8.42)

46.460

(34.06)

-0.15151

(-7.74)

0.00339

(12.90)

0.01347

(10.86)

0.517

Note: t-ratios in parentheses. Source: George and Longstaff (1993). Reprinted with the permission of

the School of Business Administration, University of Washington.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 35

Adjusted R2  60%

1 and 1 measure the tick size constraint on the spread

2 and 2 measure the effect of the option price on the spread

3 and 3 measure the effect of trading activity on the spread

4 and 4 measure the effect of time to maturity on the spread

5 and 5 measure the effect of risk on the spread

1 and 1 measure the effect of the spread size on trading activity etc.

Comments:

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 36

• The paper argues that calls and puts might be viewed as substitutes

since they are all written on the same underlying.

• So call trading activity might depend on the put spread and put trading

activity might depend on the call spread.

• The results for the other variables are little changed.

Calls and Puts as Substitutes

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 37

• Bid - Ask spread variations between options can be explained by reference to the level of trading activity, deltas, time to maturity etc. There is a 2 way relationship between volume and the spread.

• The authors argue that in the second part of the paper, they did indeed find evidence of substitutability between calls & puts.

Comments

- No diagnostics.

- Why do the CL and PL equations not contain the CR and PR variables?

- The authors could have tested for endogeneity of CBA and CL.

- Why are the squared terms in maturity and moneyness only in the

liquidity regressions?

- Wrong sign on the squared deltas.

Conclusions

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 38

• A natural generalisation of autoregressive models popularised by Sims

• A VAR is in a sense a systems regression model i.e. there is more than one dependent variable.

• Simplest case is a bivariate VAR

where uit is an iid disturbance term with E(uit)=0, i=1,2; E(u1t u2t)=0.

• The analysis could be extended to a VAR(g) model, or so that there are g variables and g equations.

Vector Autoregressive Models

y y y y y u

y y y y y u

t t k t k t k t k t

t t k t k t k t k t

1 10 11 1 1 1 1 11 2 1 1 2 1

2 20 21 2 1 2 2 21 1 1 2 1 2

       

       

   

   

    

    

... ...

... ...

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 39

• One important feature of VARs is the compactness with which we can write the notation. For example, consider the case from above where k=1.

• We can write this as

or

or even more compactly as

yt = 0 + 1 yt-1 + ut

g1 g1 gg g1 g1

Vector Autoregressive Models:

Notation and Concepts

y y y u

y y y u

t t t t

t t t t

1 10 11 1 1 11 2 1 1

2 20 21 2 1 21 1 1 2

   

   

 

 

  

  

y

y

y

y

u

u

t

t

t

t

t

t

1

2

10

20

11 11

21 21

1 1

2 1

1

2

 

  

 

  

 

  

 

  

 

 

 

 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 40

• This model can be extended to the case where there are k lags of each

variable in each equation:

yt = 0 + 1 yt-1 + 2 yt-2 +...+ k yt-k + ut

g1 g1 gg g1 gg g1 gg g1 g1

• We can also extend this to the case where the model includes first

difference terms and cointegrating relationships (a VECM).

Vector Autoregressive Models:

Notation and Concepts (cont’d)

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 41

• Advantages of VAR Modelling

- Do not need to specify which variables are endogenous or exogenous - all are endogenous

- Allows the value of a variable to depend on more than just its own lags or combinations of white noise terms, so more general than ARMA modelling

- Provided that there are no contemporaneous terms on the right hand side of the equations, can simply use OLS separately on each equation

- Forecasts are often better than “traditional structural” models.

• Problems with VAR‟s

- VAR‟s are a-theoretical (as are ARMA models)

- How do you decide the appropriate lag length?

- So many parameters! If we have g equations for g variables and we have k lags of each of the variables in each equation, we have to estimate (g+kg2) parameters. e.g. g=3, k=3, parameters = 30

- Do we need to ensure all components of the VAR are stationary?

- How do we interpret the coefficients?

Vector Autoregressive Models Compared with

Structural Equations Models

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 42

Choosing the Optimal Lag Length for a VAR

 2 possible approaches: cross-equation restrictions and information criteria

Cross-Equation Restrictions

 In the spirit of (unrestricted) VAR modelling, each equation should have

the same lag length

 Suppose that a bivariate VAR(8) estimated using quarterly data has 8 lags

of the two variables in each equation, and we want to examine a restriction

that the coefficients on lags 5 through 8 are jointly zero. This can be done

using a likelihood ratio test

 Denote the variance-covariance matrix of residuals (given by /T), as .

The likelihood ratio test for this joint hypothesis is given by

̂uu ˆˆ

 urTLR  ˆlogˆlog

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 43

Choosing the Optimal Lag Length for a VAR

(cont’d)

where is the variance-covariance matrix of the residuals for the restricted

model (with 4 lags), is the variance-covariance matrix of residuals for the

unrestricted VAR (with 8 lags), and T is the sample size.

• The test statistic is asymptotically distributed as a 2 with degrees of freedom

equal to the total number of restrictions. In the VAR case above, we are

restricting 4 lags of two variables in each of the two equations = a total of 4 *

2 * 2 = 16 restrictions.

• In the general case where we have a VAR with p equations, and we want to

impose the restriction that the last q lags have zero coefficients, there would

be p2q restrictions altogether

• Disadvantages: Conducting the LR test is cumbersome and requires a

normality assumption for the disturbances.

r̂

u̂

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 44

Information Criteria for VAR Lag Length Selection

• Multivariate versions of the information criteria are required. These can

be defined as:

where all notation is as above and k is the total number of regressors in all

equations, which will be equal to g2k + g for g equations, each with k lags

of the g variables, plus a constant term in each equation. The values of the

information criteria are constructed for 0, 1, … lags (up to some pre-

specified maximum ).

k

ln(ln(T)) 2ˆln

ln(T)ˆln

/2ˆln

T

k MHQIC

T

k MSBIC

TkMAIC

 

 



„Introductory Econometrics for Finance‟ © Chris Brooks 2002 45

Does the VAR Include Contemporaneous Terms?

• So far, we have assumed the VAR is of the form

• But what if the equations had a contemporaneous feedback term?

• We can write this as

• This VAR is in primitive form.

y y y u

y y y u

t t t t

t t t t

1 10 11 1 1 11 2 1 1

2 20 21 2 1 21 1 1 2

   

   

 

 

  

  

y y y y u

y y y y u

t t t t t

t t t t t

1 10 11 1 1 11 2 1 12 2 1

2 20 21 2 1 21 1 1 22 1 2

    

    

 

 

   

   

y

y

y

y

y

y

u

u

t

t

t

t

t

t

t

t

1

2

10

20

11 11

21 21

1 1

2 1

12

22

2

1

1

20

0

 

  

 

  

 

  

 

  

 

  

 

  

 

 

 

 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 46

Primitive versus Standard Form VARs

• We can take the contemporaneous terms over to the LHS and write

or

B yt = 0 + 1 yt-1 + ut

• We can then pre-multiply both sides by B-1 to give

yt = B-10 + B-11 yt-1 + B-1ut

or

yt = A0 + A1 yt-1 + et

• This is known as a standard form VAR, which we can estimate using OLS.

1

122

12 1

2

10

20

11 11

21 21

1 1

2 1

1

2



 

  

 

  

 

  

 

  

 

  

 

 



 

 

 

y

y

y

y

u

u

t

t

t

t

t

t

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 47

Block Significance and Causality Tests

• It is likely that, when a VAR includes many lags of variables, it will be difficult to see which sets of variables have significant effects on each dependent variable and which do not. For illustration, consider the following bivariate VAR(3):

• This VAR could be written out to express the individual equations as

• We might be interested in testing the following hypotheses, and their implied restrictions on the parameter matrices:

 

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

 

  

t

t

t

t

t

t

t

t

t

t

u

u

y

y

y

y

y

y

y

y

2

1

32

31

2221

1211

22

21

2221

1211

12

11

2221

1211

20

10

2

1













tttttttt

tttttttt

uyyyyyyy

uyyyyyyy

2322231212222212112221121202

1321231112212211112121111101













„Introductory Econometrics for Finance‟ © Chris Brooks 2002 48

Block Significance and Causality Tests (cont’d)

• Each of these four joint hypotheses can be tested within the F-test framework, since each set of restrictions contains only parameters drawn from one equation.

• These tests could also be referred to as Granger causality tests.

• Granger causality tests seek to answer questions such as “Do changes in y1 cause changes in y2?” If y1 causes y2, lags of y1 should be significant in the equation for y2. If this is the case, we say that y1 “Granger-causes” y2.

• If y2 causes y1, lags of y2 should be significant in the equation for y1.

• If both sets of lags are significant, there is “bi-directional causality”

Hypothesis Implied Restriction

1. Lags of y1t do not explain current y2t 21 = 0 and 21 = 0 and 21 = 0

2. Lags of y1t do not explain current y1t 11 = 0 and 11 = 0 and 11 = 0

3. Lags of y2t do not explain current y1t 12 = 0 and 12 = 0 and 12 = 0

4. Lags of y2t do not explain current y2t 22 = 0 and 22 = 0 and 22 = 0

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 49

Impulse Responses

• VAR models are often difficult to interpret: one solution is to construct

the impulse responses and variance decompositions.

• Impulse responses trace out the responsiveness of the dependent variables

in the VAR to shocks to the error term. A unit shock is applied to each

variable and its effects are noted.

• Consider for example a simple bivariate VAR(1):

• A change in u1t will immediately change y1. It will change change y2 and

also y1 during the next period.

• We can examine how long and to what degree a shock to a given equation

has on all of the variables in the system.

y y y u

y y y u

t t t t

t t t t

1 10 11 1 1 11 2 1 1

2 20 21 2 1 21 1 1 2

   

   

 

 

  

  

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 50

Variance Decompositions

• Variance decompositions offer a slightly different method of examining

VAR dynamics. They give the proportion of the movements in the

dependent variables that are due to their “own” shocks, versus shocks to the

other variables.

• This is done by determining how much of the s-step ahead forecast error

variance for each variable is explained innovations to each explanatory

variable (s = 1,2,…).

• The variance decomposition gives information about the relative importance

of each shock to the variables in the VAR.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 51

Impulse Responses and Variance Decompositions:

The Ordering of the Variables

• But for calculating impulse responses and variance decompositions, the

ordering of the variables is important.

• The main reason for this is that above, we assumed that the VAR error terms

were statistically independent of one another.

• This is generally not true, however. The error terms will typically be correlated

to some degree.

• Therefore, the notion of examining the effect of the innovations separately has

little meaning, since they have a common component.

• What is done is to “orthogonalise” the innovations.

• In the bivariate VAR, this problem would be approached by attributing all of

the effect of the common component to the first of the two variables in the

VAR.

• In the general case where there are more variables, the situation is more

complex but the interpretation is the same.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 52

An Example of the use of VAR Models:

The Interaction between Property Returns and the

Macroeconomy. • Brooks and Tsolacos (1999) employ a VAR methodology for investigating the

interaction between the UK property market and various macroeconomic variables.

• Monthly data are used for the period December 1985 to January 1998.

• It is assumed that stock returns are related to macroeconomic and business

conditions.

• The variables included in the VAR are

– FTSE Property Total Return Index (with general stock market effects removed)

– The rate of unemployment

– Nominal interest rates

– The spread between long and short term interest rates

– Unanticipated inflation

– The dividend yield.

The property index and unemployment are I(1) and hence are differenced.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 53

Marginal Significance Levels associated with Joint

F-tests that all 14 Lags have not Explanatory Power

for that particular Equation in the VAR

• Multivariate AIC selected 14 lags of each variable in the VAR

Lags of Variable

Dependent variable SIR DIVY SPREAD UNEM UNINFL PROPRES

SIR 0.0000 0.0091 0.0242 0.0327 0.2126 0.0000

DIVY 0.5025 0.0000 0.6212 0.4217 0.5654 0.4033

SPREAD 0.2779 0.1328 0.0000 0.4372 0.6563 0.0007

UNEM 0.3410 0.3026 0.1151 0.0000 0.0758 0.2765

UNINFL 0.3057 0.5146 0.3420 0.4793 0.0004 0.3885

PROPRES 0.5537 0.1614 0.5537 0.8922 0.7222 0.0000

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 54

Variance Decompositions for the

Property Sector Index Residuals

• Ordering for Variance Decompositions and Impulse Responses:

– Order I: PROPRES, DIVY, UNINFL, UNEM, SPREAD, SIR

– Order II: SIR, SPREAD, UNEM, UNINFL, DIVY, PROPRES.

Explained by innovations in

SIR DIVY SPREAD UNEM UNINFL PROPRES

Months ahead I II I II I II I II I II I II

1 0.0 0.8 0.0 38.2 0.0 9.1 0.0 0.7 0.0 0.2 100.0 51.0

2 0.2 0.8 0.2 35.1 0.2 12.3 0.4 1.4 1.6 2.9 97.5 47.5

3 3.8 2.5 0.4 29.4 0.2 17.8 1.0 1.5 2.3 3.0 92.3 45.8

4 3.7 2.1 5.3 22.3 1.4 18.5 1.6 1.1 4.8 4.4 83.3 51.5

12 2.8 3.1 15.5 8.7 15.3 19.5 3.3 5.1 17.0 13.5 46.1 50.0

24 8.2 6.3 6.8 3.9 38.0 36.2 5.5 14.7 18.1 16.9 23.4 22.0

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 55

Impulse Responses and Standard Error Bands for

Innovations in Dividend Yield and

the Treasury Bill Yield

Innovations in Dividend Yields

-0.06

-0.04

-0.02

0

0.02

0.04

0.06

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Steps Ahead

Innovations in the T-Bill Yield

-0.08

-0.06

-0.04

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0

0.02

0.04

0.06

0.08

0.1

0.12

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Steps Ahead

Topic3.pdf

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 1

Topic 3

Non-Stationary Time Series

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 2

Stationarity and Unit Root Testing

Why do we need to test for Non-Stationarity?

• The stationarity or otherwise of a series can strongly influence its behaviour and properties - e.g. persistence of shocks will be infinite for nonstationary series

• Spurious regressions. If two variables are trending over time, a regression of one on the other could have a high R2 even if the two are totally unrelated

• If the variables in the regression model are not stationary, then it can be proved that the standard assumptions for asymptotic analysis will not be valid. In other words, the usual “t-ratios” will not follow a t- distribution, so we cannot validly undertake hypothesis tests about the regression parameters.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 3

Value of R2 for 1000 Sets of Regressions of a

Non-stationary Variable on another Independent

Non-stationary Variable

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 4

Value of t-ratio on Slope Coefficient for 1000 Sets of

Regressions of a Non-stationary Variable on another

Independent Non-stationary Variable

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 5

Two types of Non-Stationarity

• Various definitions of non-stationarity exist

• In this chapter, we are really referring to the weak form or covariance stationarity

• There are two models which have been frequently used to characterise non-stationarity: the random walk model with drift:

yt =  + yt-1 + ut (1)

and the deterministic trend process:

yt =  + t + ut (2)

where ut is iid in both cases.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 6

Stochastic Non-Stationarity

• Note that the model (1) could be generalised to the case where yt is an

explosive process:

yt =  + yt-1 + ut

where  > 1.

• Typically, the explosive case is ignored and we use  = 1 to

characterise the non-stationarity because

–  > 1 does not describe many data series in economics and finance.

–  > 1 has an intuitively unappealing property: shocks to the system

are not only persistent through time, they are propagated so that a

given shock will have an increasingly large influence.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 7

Stochastic Non-stationarity: The Impact of Shocks

• To see this, consider the general case of an AR(1) with no drift:

yt = yt-1 + ut (3)

Let  take any value for now.

• We can write: yt-1 = yt-2 + ut-1

yt-2 = yt-3 + ut-2

• Substituting into (3) yields: yt = (yt-2 + ut-1) + ut

= 2yt-2 + ut-1 + ut

• Substituting again for yt-2: yt = 2(yt-3 + ut-2) + ut-1 + ut

= 3 yt-3 + 2ut-2 + ut-1 + ut

• Successive substitutions of this type lead to:

yt = T y0 + ut-1 + 2ut-2 + 3ut-3 + ...+ Tu0 + ut

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 8

The Impact of Shocks for

Stationary and Non-stationary Series

• We have 3 cases:

1. <1  T0 as T

So the shocks to the system gradually die away.

2. =1  T =1 T

So shocks persist in the system and never die away. We obtain:

as T

So just an infinite sum of past shocks plus some starting value of y0.

3. >1. Now given shocks become more influential as time goes on, since if >1, 3>2> etc.

 

 0

0

i

tt uyy

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 9

Detrending a Stochastically Non-stationary Series

• Going back to our 2 characterisations of non-stationarity, the r.w. with drift: yt =  + yt-1 + ut (1)

and the trend-stationary process

yt =  + t + ut (2)

• The two will require different treatments to induce stationarity. The second case is known as deterministic non-stationarity and what is required is detrending.

• The first case is known as stochastic non-stationarity. If we let yt = yt - yt-1

and L yt = yt-1

so (1-L) yt = yt - L yt = yt - yt-1

If we take (1) and subtract yt-1 from both sides:

yt - yt-1 =  + ut

yt =  + ut

We say that we have induced stationarity by “differencing once”.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 10

Detrending a Series: Using the Right Method

• Although trend-stationary and difference-stationary series are both

“trending” over time, the correct approach needs to be used in each case.

• If we first difference the trend-stationary series, it would “remove” the

non-stationarity, but at the expense on introducing an MA(1) structure into

the errors.

• Conversely if we try to detrend a series which has stochastic trend, then we

will not remove the non-stationarity.

• We will now concentrate on the stochastic non-stationarity model since

deterministic non-stationarity does not adequately describe most series in

economics or finance.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 11

Sample Plots for various Stochastic Processes:

A White Noise Process

-4

-3

-2

-1

0

1

2

3

4

1 40 79 118 157 196 235 274 313 352 391 430 469

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 12

Sample Plots for various Stochastic Processes:

A Random Walk and a Random Walk with Drift

-20

-10

0

10

20

30

40

50

60

70

1 19 37 55 73 91 109 127 145 163 181 199 217 235 253 271 289 307 325 343 361 379 397 415 433 451 469 487

Random Walk

Random Walk with Drift

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 13

Sample Plots for various Stochastic Processes:

A Deterministic Trend Process

-5

0

5

10

15

20

25

30

1 40 79 118 157 196 235 274 313 352 391 430 469

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 14

Autoregressive Processes with

differing values of  (0, 0.8, 1)

-20

-15

-10

-5

0

5

10

15

1 53 105 157 209 261 313 365 417 469 521 573 625 677 729 781 833 885 937 989

Phi=1

Phi=0.8

Phi=0

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 15

Definition of Non-Stationarity

• Consider again the simplest stochastic trend model:

yt = yt-1 + ut

or yt = ut

• We can generalise this concept to consider the case where the series contains more than one “unit root”. That is, we would need to apply the first difference operator, , more than once to induce stationarity.

Definition

If a non-stationary series, yt must be differenced d times before it becomes stationary, then it is said to be integrated of order d. We write yt I(d).

So if yt  I(d) then dyt I(0).

An I(0) series is a stationary series

An I(1) series contains one unit root,

e.g. yt = yt-1 + ut

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 16

Characteristics of I(0), I(1) and I(2) Series

• An I(2) series contains two unit roots and so would require differencing

twice to induce stationarity.

• I(1) and I(2) series can wander a long way from their mean value and

cross this mean value rarely.

• I(0) series should cross the mean frequently.

• The majority of economic and financial series contain a single unit root,

although some are stationary and consumer prices have been argued to

have 2 unit roots.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 17

How do we test for a unit root?

• The early and pioneering work on testing for a unit root in time series

was done by Dickey and Fuller (Dickey and Fuller 1979, Fuller 1976).

The basic objective of the test is to test the null hypothesis that  =1 in:

yt = yt-1 + ut

against the one-sided alternative  <1. So we have

H0: series contains a unit root

vs. H1: series is stationary.

• We usually use the regression:

yt = yt-1 + ut

so that a test of =1 is equivalent to a test of =0 (since -1=).

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 18

Different forms for the DF Test Regressions

• Dickey Fuller tests are also known as  tests: , , .

• The null (H0) and alternative (H1) models in each case are

i) H0: yt = yt-1+ut

H1: yt = yt-1+ut, <1

This is a test for a random walk against a stationary autoregressive process of order one (AR(1))

ii) H0: yt = yt-1+ut

H1: yt = yt-1++ut, <1

This is a test for a random walk against a stationary AR(1) with drift.

iii) H0: yt = yt-1+ut

H1: yt = yt-1++t+ut, <1

This is a test for a random walk against a stationary AR(1) with drift and a time trend.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 19

Computing the DF Test Statistic

• We can write

yt=ut

where yt = yt- yt-1, and the alternatives may be expressed as

yt = yt-1++t +ut

with ==0 in case i), and =0 in case ii) and =-1. In each case, the tests are based on the t-ratio on the yt-1 term in the estimated regression of yt on yt-1, plus a constant in case ii) and a constant and trend in case iii). The test statistics are defined as

test statistic =

• The test statistic does not follow the usual t-distribution under the null, since the null is one of non-stationarity, but rather follows a non-standard distribution. Critical values are derived from Monte Carlo experiments in, for example, Fuller (1976). Relevant examples of the distribution are shown in table 4.1 below

 

SE( )

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 20

Critical Values for the DF Test

The null hypothesis of a unit root is rejected in favour of the stationary alternative

in each case if the test statistic is more negative than the critical value.

Significance level 10% 5% 1%

C.V. for constant

but no trend

-2.57 -2.86 -3.43

C.V. for constant

and trend

-3.12 -3.41 -3.96

Table 4.1: Critical Values for DF and ADF Tests (Fuller,

1976, p373).

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 21

The Augmented Dickey Fuller (ADF) Test

• The tests above are only valid if ut is white noise. In particular, ut will be

autocorrelated if there was autocorrelation in the dependent variable of the

regression (yt) which we have not modelled. The solution is to “augment”

the test using p lags of the dependent variable. The alternative model in

case (i) is now written:

• The same critical values from the DF tables are used as before. A problem

now arises in determining the optimal number of lags of the dependent

variable.

There are 2 ways

- use the frequency of the data to decide

- use information criteria

 

  p

i

tititt uyyy 1

1 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 22

Testing for Higher Orders of Integration

• Consider the simple regression:

yt = yt-1 + ut

We test H0: =0 vs. H1: <0.

• If H0 is rejected we simply conclude that yt does not contain a unit root.

• But what do we conclude if H0 is not rejected? The series contains a unit

root, but is that it? No! What if ytI(2)? We would still not have rejected. So

we now need to test

H0: ytI(2) vs. H1: ytI(1)

We would continue to test for a further unit root until we rejected H0.

• We now regress 2yt on yt-1 (plus lags of 2yt if necessary).

• Now we test H0: ytI(1) which is equivalent to H0: ytI(2).

• So in this case, if we do not reject (unlikely), we conclude that yt is at least

I(2).

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 23

The Phillips-Perron Test

• Phillips and Perron have developed a more comprehensive theory of

unit root nonstationarity. The tests are similar to ADF tests, but they

incorporate an automatic correction to the DF procedure to allow for

autocorrelated residuals.

• The tests usually give the same conclusions as the ADF tests, and the

calculation of the test statistics is complex.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 24

Criticism of Dickey-Fuller and

Phillips-Perron-type tests

• Main criticism is that the power of the tests is low if the process is stationary but with a root close to the non-stationary boundary.

e.g. the tests are poor at deciding if

=1 or =0.95,

especially with small sample sizes.

• If the true data generating process (dgp) is

yt = 0.95yt-1 + ut

then the null hypothesis of a unit root should be rejected.

• One way to get around this is to use a stationarity test as well as the unit root tests we have looked at.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 25

Stationarity tests

• Stationarity tests have

H0: yt is stationary

versus H1: yt is non-stationary

So that by default under the null the data will appear stationary.

• One such stationarity test is the KPSS test (Kwaitowski, Phillips, Schmidt and Shin, 1992).

• Thus we can compare the results of these tests with the ADF/PP procedure to see if we obtain the same conclusion.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 26

Stationarity tests (cont’d)

• A Comparison

ADF / PP KPSS

H0: yt  I(1) H0: yt  I(0)

H1: yt  I(0) H1: yt  I(1)

• 4 possible outcomes

Reject H0 and Do not reject H0

Do not reject H0 and Reject H0

Reject H0 and Reject H0

Do not reject H0 and Do not reject H0

Topic4.pdf

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 1

Topic 4

Cointegration and Error-Correction Model

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 2

Cointegration: An Introduction

• In most cases, if we combine two variables which are I(1), then the

combination will also be I(1).

• More generally, if we combine variables with differing orders of integration, the combination will have an order of integration equal to the largest. i.e.,

if Xi,t  I(di) for i = 1,2,3,...,k

so we have k variables each integrated of order di.

Let (1)

Then zt  I(max di)

z Xt i i t i

k

   ,

1

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 3

Linear Combinations of Non-stationary Variables

• Rearranging (1), we can write

where

• This is just a regression equation.

• But the disturbances would have some very undesirable properties: zt´ is

not stationary and is autocorrelated if all of the Xi are I(1).

• We want to ensure that the disturbances are I(0). Under what circumstances

will this be the case?

   i

i t

t z

z i k   

1 1 2, ' , ,...,

X X zt i i t t i

k

1 2

, , '  



„Introductory Econometrics for Finance‟ © Chris Brooks 2002 4

Definition of Cointegration (Engle & Granger, 1987)

• Let zt be a k1 vector of variables, then the components of zt are cointegrated

of order (d,b) if

i) All components of zt are I(d)

ii) There is at least one vector of coefficients  such that  zt  I(d-b)

• Many time series are non-stationary but “move together” over time.

• If variables are cointegrated, it means that a linear combination of them will be stationary.

• There may be up to r linearly independent cointegrating relationships (where r  k-1), also known as cointegrating vectors. r is also known as the cointegrating rank of zt.

• A cointegrating relationship may also be seen as a long term relationship.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 5

Cointegration and Equilibrium

• Examples of possible Cointegrating Relationships in finance:

– spot and futures prices

– ratio of relative prices and an exchange rate

– equity prices and dividends

• Market forces arising from no arbitrage conditions should ensure an

equilibrium relationship.

• No cointegration implies that series could wander apart without bound

in the long run.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 6

Equilibrium Correction or Error Correction Models

• When the concept of non-stationarity was first considered, a usual

response was to independently take the first differences of a series of I(1) variables.

• The problem with this approach is that pure first difference models have no long run solution.

e.g. Consider yt and xt both I(1).

The model we may want to estimate is

 yt = xt + ut

But this collapses to nothing in the long run.

• The definition of the long run that we use is where yt = yt-1 = y; xt = xt-1 = x.

• Hence all the difference terms will be zero, i.e.  yt = 0; xt = 0.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 7

Specifying an ECM

• One way to get around this problem is to use both first difference and

levels terms, e.g.

 yt = 1xt + 2(yt-1-xt-1) + ut (2)

• yt-1-xt-1 is known as the error correction term.

• Providing that yt and xt are cointegrated with cointegrating coefficient

, then (yt-1-xt-1) will be I(0) even though the constituents are I(1).

• We can thus validly use OLS on (2).

• The Granger representation theorem shows that any cointegrating

relationship can be expressed as an equilibrium correction model.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 8

Testing for Cointegration in Regression

• The model for the equilibrium correction term can be generalised to

include more than two variables:

yt = 1 + 2x2t + 3x3t + … + kxkt + ut (3)

• ut should be I(0) if the variables yt, x2t, ... xkt are cointegrated.

• So what we want to test is the residuals of equation (3) to see if they are non-stationary or stationary. We can use the DF / ADF test on ut.

So we have the regression

with vt  iid.

• However, since this is a test on the residuals of an actual model, , then the critical values are changed.

  u u vt t t  1

ut

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 9

Testing for Cointegration in Regression:

Conclusions

• Engle and Granger (1987) have tabulated a new set of critical values

and hence the test is known as the Engle Granger (E.G.) test.

• We can also use the Durbin Watson test statistic or the Phillips Perron

approach to test for non-stationarity of .

• What are the null and alternative hypotheses for a test on the residuals

of a potentially cointegrating regression?

H0 : unit root in cointegrating regression‟s residuals

H1 : residuals from cointegrating regression are stationary

ut

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 10

Methods of Parameter Estimation in

Cointegrated Systems:

The Engle-Granger Approach

• There are (at least) 3 methods we could use: Engle Granger, Engle and Yoo, and Johansen.

• The Engle Granger 2 Step Method

This is a single equation technique which is conducted as follows:

Step 1:

- Make sure that all the individual variables are I(1).

- Then estimate the cointegrating regression using OLS.

- Save the residuals of the cointegrating regression, .

- Test these residuals to ensure that they are I(0).

Step 2:

- Use the step 1 residuals as one variable in the error correction model e.g.

 yt = 1xt + 2( ) + ut

where = yt-1- xt-1

1 ˆ t

u

1 ˆ t

u

ut

̂

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 11

An Example of a Model for Non-stationary

Variables: Lead-Lag Relationships between Spot

and Futures Prices

Background

• We expect changes in the spot price of a financial asset and its corresponding futures price to be perfectly contemporaneously correlated and not to be cross-autocorrelated.

i.e. expect Corr(ln(Ft),ln(St))  1

Corr(ln(Ft),ln(St-k))  0  k

Corr(ln(Ft-j),ln(St))  0  j

• We can test this idea by modelling the lead-lag relationship between the two.

• We will consider two papers Tse(1995) and Brooks et al (2001).

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 12

Futures & Spot Data

• Tse (1995): 1055 daily observations on NSA stock index and stock

index futures values from December 1988 - April 1993.

• Brooks et al (2001): 13,035 10-minutely observations on the FTSE

100 stock index and stock index futures prices for all trading days in

the period June 1996 – 1997.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 13

Methodology

• The fair futures price is given by

where Ft * is the fair futures price, St is the spot price, r is a

continuously compounded risk-free rate of interest, d is the

continuously compounded yield in terms of dividends derived from the

stock index until the futures contract matures, and (T-t) is the time to

maturity of the futures contract. Taking logarithms of both sides of

equation above gives

• First, test ft and st for nonstationarity.

t *

t (r-d)(T-t)F = S e

t)-d)(T-(r s f tt *

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 14

Dickey-Fuller Tests on Log-Prices and Returns for

High Frequency FTSE Data

Futures Spot

Dickey-Fuller Statistics

for Log-Price Data

-0.1329 -0.7335

Dickey Fuller Statistics

for Returns Data

-84.9968 -114.1803

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 15

Cointegration Test Regression and Test on Residuals

• Conclusion: log Ft and log St are not stationary, but log Ft and log St are stationary.

• But a model containing only first differences has no long run relationship.

• Solution is to see if there exists a cointegrating relationship between ft and st which would mean that we can validly include levels terms in this framework.

• Potential cointegrating regression:

where zt is a disturbance term.

• Estimate the regression, collect the residuals, , and test whether they are stationary.

zt

ttt zfs  10 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 16

Estimated Equation and Test for Cointegration for

High Frequency FTSE Data

Cointegrating Regression

Coefficient  0

 1

Estimated Value

0.1345

0.9834

DF Test on residuals tẑ

Test Statistic

-14.7303

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 17

Conclusions from Unit Root and Cointegration Tests

• Conclusion: are stationary and therefore we have a cointegrating

relationship between log Ft and log St.

• Final stage in Engle-Granger 2-step method is to use the first stage

residuals, as the equilibrium correction term in the general equation.

• The overall model is

zt

zt

ttttt vFSzS   111110 lnlnˆln 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 18

Estimated Error Correction Model for

High Frequency FTSE Data

Look at the signs and significances of the coefficients:

• is positive and highly significant

• is positive and highly significant

• is negative and highly significant

Coefficient Estimated Value t-ratio 0

9.6713E-06 1.6083

 -8.3388E-01 -5.1298

1 0.1799 19.2886

1 0.1312 20.4946

1̂

1̂



„Introductory Econometrics for Finance‟ © Chris Brooks 2002 19

The Engle-Granger Approach: Some Drawbacks

This method suffers from a number of problems:

1. Unit root and cointegration tests have low power in finite samples

2. We are forced to treat the variables asymmetrically and to specify one as the dependent and the other as independent variables.

3. Cannot perform any hypothesis tests about the actual cointegrating relationship estimated at stage 1.

- Problem 1 is a small sample problem that should disappear asymptotically.

- Problem 2 is addressed by the Johansen approach.

- Problem 3 is addressed by the Engle and Yoo approach or the Johansen approach.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 20

• One of the problems with the EG 2-step method is that we cannot make any inferences about the actual cointegrating regression.

• The Engle & Yoo (EY) 3-step procedure takes its first two steps from EG.

• EY add a third step giving updated estimates of the cointegrating vector and its standard errors.

• The most important problem with both these techniques is that in the general case above, where we have more than two variables which may be cointegrated, there could be more than one cointegrating relationship.

• In fact there can be up to r linearly independent cointegrating vectors

(where r  g-1), where g is the number of variables in total.

The Engle & Yoo 3-Step Method

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 21

• So, in the case where we just had y and x, then r can only be one or

zero.

• But in the general case there could be more cointegrating relationships.

• And if there are others, how do we know how many there are or

whether we have found the “best”?

• The answer to this is to use a systems approach to cointegration which

will allow determination of all r cointegrating relationships -

Johansen‟s method.

The Engle & Yoo 3-Step Method (cont’d)

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 22

• To use Johansen‟s method, we need to turn the VAR of the form

yt = 1 yt-1 + 2 yt-2 +...+ k yt-k + ut

g×1 g×g g×1 g×g g×1 g×g g×1 g×1

into a VECM, which can be written as

yt =  yt-k + 1 yt-1 + 2 yt-2 + ... + k-1 yt-(k-1) + ut

where  = and

 is a long run coefficient matrix since all the yt-i = 0.

Testing for and Estimating Cointegrating Systems

Using the Johansen Technique Based on VARs

 

 k

j gi I

1

)(   

 i

j

gji I 1

)( 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 23

• Let  denote a gg square matrix and let c denote a g1 non-zero vector, and let  denote a set of scalars.

•  is called a characteristic root or set of roots of  if we can write

 c =  c

gg g1 g1

• We can also write

 c =  Ip c

and hence

(  - Ig ) c = 0

where Ig is an identity matrix.

Review of Matrix Algebra

necessary for the Johansen Test

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 24

• Since c  0 by definition, then for this system to have zero solution, we

require the matrix (  - Ig ) to be singular (i.e. to have zero determinant).

  - Ig  = 0

• For example, let  be the 2  2 matrix

• Then the characteristic equation is

  - Ig 

Review of Matrix Algebra (cont’d)

  

 

 

5 1

2 4

 

 

  

 

  

 

       

5 1

2 4

1 0

0 1 0

5 1

2 4 5 4 2 9 182

    ( )( )

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 25

• This gives the solutions  = 6 and  = 3.

• The characteristic roots are also known as Eigenvalues.

• The rank of a matrix is equal to the number of linearly independent rows or columns in the matrix.

• We write Rank () = r

• The rank of a matrix is equal to the order of the largest square matrix we can obtain from  which has a non-zero determinant.

• For example, the determinant of  above  0, therefore it has rank 2.

Review of Matrix Algebra (cont’d)

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 26

• Some properties of the eigenvalues of any square matrix A:

1. the sum of the eigenvalues is the trace

2. the product of the eigenvalues is the determinant

3. the number of non-zero eigenvalues is the rank

• Returning to Johansen‟s test, the VECM representation of the VAR was

yt =  yt-1 + 1 yt-1 + 2 yt-2 + ... + k-1 yt-(k-1) + ut

• The test for cointegration between the y‟s is calculated by looking at the rank of the  matrix via its eigenvalues. (To prove this requires some technical intermediate steps).

• The rank of a matrix is equal to the number of its characteristic roots (eigenvalues) that are different from zero.

The Johansen Test and Eigenvalues

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 27

• The eigenvalues denoted i are put in order:

1  2  ...  g

• If the variables are not cointegrated, the rank of  will not be

significantly different from zero, so i = 0  i.

Then if i = 0, ln(1-i) = 0

If the ‟s are roots, they must be less than 1 in absolute value.

• Say rank () = 1, then ln(1-1) will be negative and ln(1-i) = 0

• If the eigenvalue i is non-zero, then ln(1-i) < 0  i > 1.

The Johansen Test and Eigenvalues (cont’d)

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 28

• The test statistics for cointegration are formulated as

and

where is the estimated value for the ith ordered eigenvalue from the  matrix.

trace tests the null that the number of cointegrating vectors is less than equal to r against an unspecified alternative.

trace = 0 when all the i = 0, so it is a joint test.

max tests the null that the number of cointegrating vectors is r against an alternative of r+1.

The Johansen Test Statistics

 max( , ) ln(  )r r T r    1 1 1

 

 g

ri

itrace Tr 1

)ˆ1ln()( 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 29

Decomposition of the  Matrix

• For any 1 < r < g,  is defined as the product of two matrices:

 = 

gg gr rg

•  contains the cointegrating vectors while  gives the “loadings” of

each cointegrating vector in each equation.

• For example, if g=4 and r=1,  and  will be 41, and yt-k will be

given by:

or

 

kt y

y

y

y

    

    

    

    



4

3

2

1

14131211

14

13

12

11



  kt

yyyy 

    

    

 414313212111

14

13

12

11



„Introductory Econometrics for Finance‟ © Chris Brooks 2002 30

• Johansen & Juselius (1990) provide critical values for the 2 statistics.

The distribution of the test statistics is non-standard. The critical values

depend on:

1. the value of g-r, the number of non-stationary components

2. whether a constant and / or trend are included in the regressions.

• If the test statistic is greater than the critical value from Johansen‟s

tables, reject the null hypothesis that there are r cointegrating vectors in

favour of the alternative that there are more than r.

Johansen Critical Values

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 31

• The testing sequence under the null is r = 0, 1, ..., g-1

so that the hypotheses for trace are

H0: r = 0 vs H1: 0 < r  g

H0: r = 1 vs H1: 1 < r  g

H0: r = 2 vs H1: 2 < r  g

... ... ...

H0: r = g-1 vs H1: r = g

• We keep increasing the value of r until we no longer reject the null.

The Johansen Testing Sequence

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 32

• But how does this correspond to a test of the rank of the  matrix?

• r is the rank of .

•  cannot be of full rank (g) since this would correspond to the original yt being stationary.

• If  has zero rank, then by analogy to the univariate case, yt depends only on yt-j and not on yt-1, so that there is no long run relationship between the elements of yt-1. Hence there is no cointegration.

• For 1 < rank () < g , there are multiple cointegrating vectors.

Interpretation of Johansen Test Results

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 33

Hypothesis Testing Using Johansen

• EG did not allow us to do hypothesis tests on the cointegrating relationship itself, but the Johansen approach does.

• If there exist r cointegrating vectors, only these linear combinations will be stationary.

• You can test a hypothesis about one or more coefficients in the cointegrating relationship by viewing the hypothesis as a restriction on the  matrix.

• All linear combinations of the cointegrating vectors are also cointegrating vectors.

• If the number of cointegrating vectors is large, and the hypothesis under consideration is simple, it may be possible to recombine the cointegrating vectors to satisfy the restrictions exactly.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 34

Hypothesis Testing Using Johansen (cont’d)

• As the restrictions become more complex or more numerous, it will eventually become impossible to satisfy them by renormalisation.

• After this point, if the restriction is not severe, then the cointegrating vectors will not change much upon imposing the restriction.

• A test statistic to test this hypothesis is given by

 2(m)

where,

are the characteristic roots of the restricted model

are the characteristic roots of the unrestricted model

r is the number of non-zero characteristic roots in the unrestricted model, and m is the number of restrictions.

i *

i

 

 r

i

iiT 1

*)]1ln()1[ln( 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 35

Cointegration Tests using Johansen:

Three Examples

Example 1: Hamilton(1994, pp.647 )

• Does the PPP relationship hold for the US / Italian exchange rate -

price system?

• A VAR was estimated with 12 lags on 189 observations. The Johansen

test statistics were

r max critical value

0 22.12 20.8

1 10.19 14.0

• Conclusion: there is one cointegrating relationship.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 36

Example 2: Purchasing Power Parity (PPP)

• PPP states that the equilibrium exchange rate between 2 countries is

equal to the ratio of relative prices

• A necessary and sufficient condition for PPP is that the log of the

exchange rate between countries A and B, and the logs of the price

levels in countries A and B be cointegrated with cointegrating vector

[ 1 –1 1] .

• Chen (1995) uses monthly data for April 1973-December 1990 to test

the PPP hypothesis using the Johansen approach.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 37

Cointegration Tests of PPP with European Data

Tests for

cointegration between

r = 0 r  1 r  2 1 2

FRF – DEM 34.63* 17.10 6.26 1.33 -2.50

FRF – ITL 52.69* 15.81 5.43 2.65 -2.52

FRF – NLG 68.10* 16.37 6.42 0.58 -0.80

FRF – BEF 52.54* 26.09* 3.63 0.78 -1.15

DEM – ITL 42.59* 20.76* 4.79 5.80 -2.25

DEM – NLG 50.25* 17.79 3.28 0.12 -0.25

DEM – BEF 69.13* 27.13* 4.52 0.87 -0.52

ITL – NLG 37.51* 14.22 5.05 0.55 -0.71

ITL – BEF 69.24* 32.16* 7.15 0.73 -1.28

NLG – BEF 64.52* 21.97* 3.88 1.69 -2.17

Critical values 31.52 17.95 8.18 - - Notes: FRF- French franc; DEM – German Mark; NLG – Dutch guilder; ITL – Italian lira; BEF –

Belgian franc. Source: Chen (1995). Reprinted with the permission of Taylor and Francis Ltd.

(www.tandf.co.uk).

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 38

Example 3: Are International

Bond Markets Cointegrated?

• Mills & Mills (1991)

• If financial markets are cointegrated, this implies that they have a “common stochastic trend”.

Data:

• Daily closing observations on redemption yields on government bonds for 4 bond markets: US, UK, West Germany, Japan.

• For cointegration, a necessary but not sufficient condition is that the yields are nonstationary. All 4 yields series are I(1).

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 39

Testing for Cointegration Between the Yields

• The Johansen procedure is used. There can be at most 3 linearly independent

cointegrating vectors.

• Mills & Mills use the trace test statistic:

where i are the ordered eigenvalues.

 

 g

ri itrace Tr

1

)ˆ1ln()( 

Johansen Tests for Cointegration between International Bond Yields

Test statistic Critical Values r (number of cointegrating

vectors under the null hypothesis) 10% 5%

0 22.06 35.6 38.6

1 10.58 21.2 23.8

2 2.52 10.3 12.0

3 0.12 2.9 4.2 Source: Mills and Mills (1991). Reprinted with the permission of Blackwell Publishers.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 40

Testing for Cointegration Between the Yields

(cont’d)

• Conclusion: No cointegrating vectors.

• The paper then goes on to estimate a VAR for the first differences of the

yields, which is of the form

where

They set k = 8.

X

X US

X UK

X WG

X JAP

t

t

t

t

t

i

i i i i

i i i i

i i i i

i i i i

t

t

t

t

t

   

   

   

   

   

   

( )

( )

( )

( )

, ,

   

   

   

   

11 12 13 14

21 22 23 24

31 32 33 34

41 42 43 44

1

2

3

4

 

  k

i

titit XX 1

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 41

Variance Decompositions for VAR

of International Bond Yields

Variance Decompositions for VAR of International Bond Yields

Explained by movements in Explaining

movements in

Days

ahead US UK Germany Japan

US 1 95.6 2.4 1.7 0.3

5 94.2 2.8 2.3 0.7

10 92.9 3.1 2.9 1.1

20 92.8 3.2 2.9 1.1

UK 1 0.0 98.3 0.0 1.7

5 1.7 96.2 0.2 1.9

10 2.2 94.6 0.9 2.3

20 2.2 94.6 0.9 2.3

Germany 1 0.0 3.4 94.6 2.0

5 6.6 6.6 84.8 3.0

10 8.3 6.5 82.9 3.6

20 8.4 6.5 82.7 3.7

Japan 1 0.0 0.0 1.4 100.0

5 1.3 1.4 1.1 96.2

10 1.5 2.1 1.8 94.6

20 1.6 2.2 1.9 94.2

Source: Mills and Mills (1991). Reprinted with the permission of Blackwell Publishers.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 42

Impulse Responses for VAR of

International Bond Yields

Impulse Responses for VAR of International Bond Yields

Response of US to innovations in

Days after shock US UK Germany Japan

0 0.98 0.00 0.00 0.00

1 0.06 0.01 -0.10 0.05

2 -0.02 0.02 -0.14 0.07

3 0.09 -0.04 0.09 0.08

4 -0.02 -0.03 0.02 0.09

10 -0.03 -0.01 -0.02 -0.01

20 0.00 0.00 -0.10 -0.01

Response of UK to innovations in

Days after shock US UK Germany Japan

0 0.19 0.97 0.00 0.00

1 0.16 0.07 0.01 -0.06

2 -0.01 -0.01 -0.05 0.09

3 0.06 0.04 0.06 0.05 4 0.05 -0.01 0.02 0.07

10 0.01 0.01 -0.04 -0.01

20 0.00 0.00 -0.01 0.00

Response of Germany to innovations in

Days after shock US UK Germany Japan

0 0.07 0.06 0.95 0.00

1 0.13 0.05 0.11 0.02

2 0.04 0.03 0.00 0.00

3 0.02 0.00 0.00 0.01

4 0.01 0.00 0.00 0.09

10 0.01 0.01 -0.01 0.02

20 0.00 0.00 0.00 0.00

Response of Japan to innovations in

Days after shock US UK Germany Japan

0 0.03 0.05 0.12 0.97

1 0.06 0.02 0.07 0.04

2 0.02 0.02 0.00 0.21

3 0.01 0.02 0.06 0.07

4 0.02 0.03 0.07 0.06

10 0.01 0.01 0.01 0.04

20 0.00 0.00 0.00 0.01

Source: Mills and Mills (1991). Reprinted with the permission of Blackwell Publishers.

Topic5.pdf

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 1

Topic 5

Modelling Volatility and Correlation

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 2

An Excursion into Non-linearity Land

• Motivation: the linear structural (and time series) models cannot

explain a number of important features common to much financial data

- leptokurtosis

- volatility clustering or volatility pooling

- leverage effects

• Our “traditional” structural model could be something like:

yt = 1 + 2x2t + ... + kxkt + ut, or more compactly y = X +

u.

• We also assumed ut  N(0,2).

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 3

A Sample Financial Asset Returns Time Series

Daily S&P 500 Returns for January 1990 – December 1999

-0.08

-0.06

-0.04

-0.02

0.00

0.02

0.04

0.06

1/01/90 11/01/93 9/01/97

Return

Date

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 4

Non-linear Models: A Definition

• Campbell, Lo and MacKinlay (1997) define a non-linear data generating process as one that can be written

yt = f(ut, ut-1, ut-2, …)

where ut is an iid error term and f is a non-linear function.

• They also give a slightly more specific definition as

yt = g(ut-1, ut-2, …)+ ut 2(ut-1, ut-2, …)

where g is a function of past error terms only and 2 is a variance term.

• Models with nonlinear g(•) are “non-linear in mean”, while those with nonlinear 2(•) are “non-linear in variance”.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 5

Types of non-linear models

• The linear paradigm is a useful one. Many apparently non-linear relationships can be made linear by a suitable transformation. On the other hand, it is likely that many relationships in finance are intrinsically non-linear.

• There are many types of non-linear models, e.g.

- ARCH / GARCH

- switching models

- bilinear models

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 6

Testing for Non-linearity

• The “traditional” tools of time series analysis (acf‟s, spectral analysis)

may find no evidence that we could use a linear model, but the data

may still not be independent.

• Portmanteau tests for non-linear dependence have been developed. The

simplest is Ramsey‟s RESET test, which took the form:

• Many other non-linearity tests are available, e.g. the “BDS test” and

the bispectrum test.

• One particular non-linear model that has proved very useful in finance

is the ARCH model due to Engle (1982).

   ... u y y y vt t t p t

p

t        0 1

2

2

3

1

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 7

Heteroscedasticity Revisited

• An example of a structural model is

with ut  N(0, ).

• The assumption that the variance of the errors is constant is known as

homoscedasticity, i.e. Var (ut) = .

• What if the variance of the errors is not constant?

- heteroscedasticity

- would imply that standard error estimates could be wrong.

• Is the variance of the errors likely to be constant over time? Not for financial data.

u

2

u

2

yt = 1 + 2x2t + 3x3t + 4x4t + u t

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 8

Autoregressive Conditionally Heteroscedastic

(ARCH) Models

• So use a model which does not assume that the variance is constant.

• Recall the definition of the variance of ut:

= Var(ut ut-1, ut-2,...) = E[(ut-E(ut)) 2 ut-1, ut-2,...]

We usually assume that E(ut) = 0

so = Var(ut  ut-1, ut-2,...) = E[ut 2 ut-1, ut-2,...].

• What could the current value of the variance of the errors plausibly depend upon?

– Previous squared error terms.

• This leads to the autoregressive conditionally heteroscedastic model for the variance of the errors:

= 0 + 1

• This is known as an ARCH(1) model.

t 2

t 2

t 2

ut1 2

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 9

Autoregressive Conditionally Heteroscedastic

(ARCH) Models (cont’d)

• The full model would be

yt = 1 + 2x2t + ... + kxkt + ut , ut  N(0, )

where = 0 + 1

• We can easily extend this to the general case where the error variance depends on q lags of squared errors:

= 0 + 1 +2 +...+q

• This is an ARCH(q) model.

• Instead of calling the variance , in the literature it is usually called ht, so the model is

yt = 1 + 2x2t + ... + kxkt + ut , ut  N(0,ht)

where ht = 0 + 1 +2 +...+q

t 2

t 2

t 2

ut1 2

ut q 2

ut q 2

t 2

2

1tu 2

2tu

2

1tu 2

2tu

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 10

Another Way of Writing ARCH Models

• For illustration, consider an ARCH(1). Instead of the above, we can

write

yt = 1 + 2x2t + ... + kxkt + ut , ut = vtt

, vt  N(0,1)

• The two are different ways of expressing exactly the same model. The

first form is easier to understand while the second form is required for

simulating from an ARCH model, for example.

  t tu  0 1 1 2

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Testing for “ARCH Effects”

1. First, run any postulated linear regression of the form given in the equation

above, e.g. yt = 1 + 2x2t + ... + kxkt + ut

saving the residuals, .

2. Then square the residuals, and regress them on q own lags to test for ARCH

of order q, i.e. run the regression

where vt is iid.

Obtain R2 from this regression

3. The test statistic is defined as TR2 (the number of observations multiplied by the coefficient of multiple correlation) from the last regression, and is distributed as a 2(q).

tû

tqtqttt vuuuu  

22

22

2

110

2 ˆ...ˆˆˆ 

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Testing for “ARCH Effects” (cont’d)

4. The null and alternative hypotheses are

H0 : 1 = 0 and 2 = 0 and 3 = 0 and ... and q = 0

H1 : 1  0 or 2  0 or 3  0 or ... or q  0.

If the value of the test statistic is greater than the critical value from the

2 distribution, then reject the null hypothesis.

• Note that the ARCH test is also sometimes applied directly to returns

instead of the residuals from Stage 1 above.

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Problems with ARCH(q) Models

• How do we decide on q?

• The required value of q might be very large

• Non-negativity constraints might be violated.

– When we estimate an ARCH model, we require i >0  i=1,2,...,q

(since variance cannot be negative)

• A natural extension of an ARCH(q) model which gets around some of

these problems is a GARCH model.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 14

Generalised ARCH (GARCH) Models

• Due to Bollerslev (1986). Allow the conditional variance to be dependent

upon previous own lags

• The variance equation is now

(1)

• This is a GARCH(1,1) model, which is like an ARMA(1,1) model for the

variance equation.

• We could also write

• Substituting into (1) for t-1 2 :

t 2 = 0 + 1

2

1tu +t-1 2

t-1 2 = 0 + 1

2

2tu +t-2 2

t-2 2 = 0 + 1

2

3tu +t-3 2

t 2 = 0 + 1

2

1tu +(0 + 1 2

2tu +t-2 2 )

= 0 + 1 2

1tu +0 + 1 2

2tu +t-2 2

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 15

Generalised ARCH (GARCH) Models (cont’d)

• Now substituting into (2) for t-2 2

• An infinite number of successive substitutions would yield

• So the GARCH(1,1) model can be written as an infinite order ARCH model.

• We can again extend the GARCH(1,1) model to a GARCH(p,q):

t 2 =0 + 1

2

1tu +0 + 1 2

2tu +2(0 + 1 2

3tu +t-3 2)

t 2 = 0 + 1

2

1tu +0 + 1 2

2tu +0 2 + 1

2 2

3tu +3t-3 2

t 2 = 0 (1++2) + 1

2

1tu (1+L+2L2 ) + 3t-3 2

t 2 = 0 (1++2+...) + 1

2

1tu (1+L+2L2+...) + 0 2

t 2 = 0+1

2

1tu +2 2

2tu +...+q 2

qtu  +1t-1 2 +2t-2

2 +...+pt-p

2

t 2 =  

 

  q

i

p

j

jtjitiu 1 1

22

0 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 16

Generalised ARCH (GARCH) Models (cont’d)

• But in general a GARCH(1,1) model will be sufficient to capture the

volatility clustering in the data.

• Why is GARCH Better than ARCH?

- more parsimonious - avoids overfitting

- less likely to breech non-negativity constraints

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 17

The Unconditional Variance under the GARCH

Specification

• The unconditional variance of ut is given by

when

• is termed “non-stationarity” in variance

• is termed intergrated GARCH

• For non-stationarity in variance, the conditional variance forecasts will

not converge on their unconditional value as the horizon increases.

Var(ut) = )(1 1

0





 1 < 1

 1  1

 1 = 1

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 18

Estimation of ARCH / GARCH Models

• Since the model is no longer of the usual linear form, we cannot use

OLS.

• We use another technique known as maximum likelihood.

• The method works by finding the most likely values of the parameters

given the actual data.

• More specifically, we form a log-likelihood function and maximise it.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 19

Estimation of ARCH / GARCH Models (cont’d)

• The steps involved in actually estimating an ARCH or GARCH model

are as follows

1. Specify the appropriate equations for the mean and the variance - e.g. an

AR(1)- GARCH(1,1) model:

2. Specify the log-likelihood function to maximise:

3. The computer will maximise the function and give parameter values and

their standard errors

yt =  + yt-1 + ut , ut  N(0,t 2)

t 2 = 0 + 1

2

1tu +t-1 2

 

 T

t

ttt

T

t

t yy T

L 1

22

1

1

2 /)(

2

1 )log(

2

1 )2log(

2 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 20

Parameter Estimation using Maximum Likelihood

• Consider the bivariate regression case with homoscedastic errors for simplicity:

• Assuming that ut  N(0,2), then yt  N( , 2) so that the probability density function for a normally distributed random variable with this mean and variance is given by

(1)

• Successive values of yt would trace out the familiar bell-shaped curve.

• Assuming that ut are iid, then yt will also be iid.

ttt uxy  21 

tx21  

  

    

2

2

212

21

)(

2

1 exp

2

1 ),(



  tt

tt

xy xyf

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 21

Parameter Estimation using Maximum Likelihood

(cont’d)

• Then the joint pdf for all the y‟s can be expressed as a product of the individual density functions

(2)

• Substituting into equation (2) for every yt from equation (1),

(3)

  

     

T

t

tt

TTtT

xy xyyyf

1 2

2

212

2121

)(

2

1 exp

)2(

1 ),,...,,(



 

 





T

t tt

T

tT

Xyf

Xyf

XyfXyfXyyyf

1

2

21

2

421

2

2212

2

1211

2

2121

),(

),(

)...,(),(),,...,,(







„Introductory Econometrics for Finance‟ © Chris Brooks 2002 22

Parameter Estimation using Maximum Likelihood

(cont’d)

• The typical situation we have is that the xt and yt are given and we want to estimate 1, 2, 

2. If this is the case, then f() is known as the likelihood function, denoted LF(1, 2, 

2), so we write

(4)

• Maximum likelihood estimation involves choosing parameter values (1, 2,

2) that maximise this function.

• We want to differentiate (4) w.r.t. 1, 2, 2, but (4) is a product containing

T terms.

  

     

T

t

tt

TT

xy LF

1 2

2

212

21

)(

2

1 exp

)2(

1 ),,(



 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 23

• Since , we can take logs of (4).

• Then, using the various laws for transforming functions containing logarithms, we obtain the log-likelihood function, LLF:

• which is equivalent to

(5)

• Differentiating (5) w.r.t. 1, 2, 2, we obtain

(6)

max ( ) maxlog( ( )) x x

f x f x

Parameter Estimation using Maximum Likelihood

(cont’d)

 

 

T

t

tt xyT TLLF

1 2

2

21 )(

2

1 )2log(

2 log

 

 

 

T

t

tt xyTT LLF

1 2

2

212 )(

2

1 )2log(

2 log

2 

 

 

 2

21

1

1.2).(

2

1





 tt xyLLF

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 24

(7)

(8)

• Setting (6)-(8) to zero to minimise the functions, and putting hats above the parameters to denote the maximum likelihood estimators,

• From (6),

(9)

Parameter Estimation using Maximum Likelihood

(cont’d)

 

 4

2

21

22

)(

2

11

2 





 tt xyTLLF

 

 2

21

2

.2).(

2

1





 ttt xxyLLF

  0)ˆˆ( 21 tt xy 

    0ˆˆ 21 tt xy 

   0ˆˆ 21 tt xTy 

   0 1ˆˆ1

21 tt x T

y T



xy 21 ˆˆ  

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 25

• From (7),

(10)

• From (8),

Parameter Estimation using Maximum Likelihood

(cont’d)

  0)ˆˆ( 21 ttt xxy 

   0ˆˆ 2

21 tttt xxxy 

   0ˆˆ 2

21 tttt xxxy 

   tttt xxyxyx )ˆ(ˆ 2

2

2 

  2

2

2

2 ˆˆ xTyxTxyx ttt 

  yxTxyxTx ttt )(ˆ 22

2

)( ˆ

222 xTx

yxTxy

t

tt

 

 

  2

2142 )ˆˆ(

ˆ

1

ˆ tt xy

T 



„Introductory Econometrics for Finance‟ © Chris Brooks 2002 26

• Rearranging,

(11)

• How do these formulae compare with the OLS estimators?

(9) & (10) are identical to OLS

(11) is different. The OLS estimator was

• Therefore the ML estimator of the variance of the disturbances is biased, although it is consistent.

• But how does this help us in estimating heteroscedastic models?

  2 21  

T ut

  2 21 

 

T k ut

Parameter Estimation using Maximum Likelihood

(cont’d)

  2

21

2 )ˆˆ( 1

ˆ tt xy

T 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 27

Estimation of GARCH Models Using

Maximum Likelihood

• Now we have yt =  + yt-1 + ut , ut  N(0, )

• Unfortunately, the LLF for a model with time-varying variances cannot be maximised analytically, except in the simplest of cases. So a numerical procedure is used to maximise the log-likelihood function. A potential problem: local optima or multimodalities in the likelihood surface.

• The way we do the optimisation is:

1. Set up LLF.

2. Use regression to get initial guesses for the mean parameters.

3. Choose some initial guesses for the conditional variance parameters.

4. Specify a convergence criterion - either by criterion or by value.

t 2

t 2 = 0 + 1

2

1tu +t-1 2

 

 T

t

ttt

T

t

t yy T

L 1

22

1

1

2 /)(

2

1 )log(

2

1 )2log(

2 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 28

Non-Normality and Maximum Likelihood

• Recall that the conditional normality assumption for ut is essential.

• We can test for normality using the following representation

ut = vtt vt  N(0,1)

• The sample counterpart is

• Are the normal? Typically are still leptokurtic, although less so than the . Is this a problem? Not really, as we can use the ML with a robust variance/covariance estimator. ML with robust standard errors is called Quasi- Maximum Likelihood or QML.

    t t tu   0 1 1 2

2 1 2 v

u t

t

t

 

t

t t

u v

̂

ˆ ˆ 

tv̂ tv̂

tû

Topic6.pdf

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 1

Topic 6

Further Topics on Volatility

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 2

Extensions to the Basic GARCH Model

• Since the GARCH model was developed, a huge number of extensions

and variants have been proposed. Three of the most important

examples are EGARCH, GJR, and GARCH-M models.

• Problems with GARCH(p,q) Models:

- Non-negativity constraints may still be violated

- GARCH models cannot account for leverage effects

• Possible solutions: the exponential GARCH (EGARCH) model or the

GJR model, which are asymmetric GARCH models.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 3

The EGARCH Model

• Suggested by Nelson (1991). The variance equation is given by

• Advantages of the model

- Since we model the log(t 2), then even if the parameters are negative, t

2

will be positive.

- We can account for the leverage effect: if the relationship between

volatility and returns is negative, , will be negative.

 

 

 

 

 

 

2 )log()log(

2

1

1

2

1

12

1

2

t

t

t

t tt

uu

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 4

The GJR Model

• Due to Glosten, Jaganathan and Runkle

where It-1 = 1 if ut-1 < 0

= 0 otherwise

• For a leverage effect, we would see  > 0.

• We require 1 +   0 and 1  0 for non-negativity.

t 2 = 0 + 1

2

1tu +t-1 2+ut-1

2It-1

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 5

An Example of the use of a GJR Model

• Using monthly S&P 500 returns, December 1979- June 1998

• Estimating a GJR model, we obtain the following results.

)198.3(

172.0ty

)772.5()999.14()437.0()372.16(

604.0498.0015.0243.1 1

2

1

2

1

2

1

2

  ttttt Iuu 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 6

News Impact Curves

The news impact curve plots the next period volatility (ht) that would arise from various

positive and negative values of ut-1, given an estimated model.

News Impact Curves for S&P 500 Returns using Coefficients from GARCH and GJR

Model Estimates:

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Value of Lagged Shock

V a lu

e o

f C

o n d

it io

n a

l V

a ri

a n

c e

GARCH

GJR

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 7

GARCH-in Mean

• We expect a risk to be compensated by a higher return. So why not let the return of a security be partly determined by its risk?

• Engle, Lilien and Robins (1987) suggested the ARCH-M specification. A GARCH-M model would be

•  can be interpreted as a sort of risk premium.

• It is possible to combine all or some of these models together to get more complex “hybrid” models - e.g. an ARMA-EGARCH(1,1)-M model.

yt =  + t-1+ ut , ut  N(0,t 2)

t 2 = 0 + 1

2

1tu +t-1 2

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 8

Testing Non-linear Restrictions or

Testing Hypotheses about Non-linear Models

• Usual t- and F-tests are still valid in non-linear models, but they are

not flexible enough.

• There are three hypothesis testing procedures based on maximum

likelihood principles: Wald, Likelihood Ratio, Lagrange Multiplier.

• Consider a single parameter,  to be estimated, Denote the MLE as

and a restricted estimate as .

~ 

̂

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 9

Likelihood Ratio Tests

• Estimate under the null hypothesis and under the alternative.

• Then compare the maximised values of the LLF.

• So we estimate the unconstrained model and achieve a given maximised value of the LLF, denoted Lu

• Then estimate the model imposing the constraint(s) and get a new value of the LLF denoted Lr.

• Which will be bigger?

• Lr  Lu comparable to RRSS  URSS

• The LR test statistic is given by

LR = -2(Lr - Lu)  2(m)

where m = number of restrictions

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 10

Likelihood Ratio Tests (cont’d)

• Example: We estimate a GARCH model and obtain a maximised LLF of 66.85. We are interested in testing whether  = 0 in the following equation.

yt =  + yt-1 + ut , ut  N(0, )

= 0 + 1 + 

• We estimate the model imposing the restriction and observe the maximised LLF falls to 64.54. Can we accept the restriction?

• LR = -2(64.54-66.85) = 4.62.

• The test follows a 2(1) = 3.84 at 5%, so reject the null.

• Denoting the maximised value of the LLF by unconstrained ML as L( )

and the constrained optimum as . Then we can illustrate the 3 testing procedures in the following diagram:

t 2

t 2 ut1

2

L( ~

)

2

1t

̂

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 11

Comparison of Testing Procedures under Maximum

Likelihood: Diagramatic Representation

 L

A

 ̂L

B

  ~

L

 ~

̂

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 12

Hypothesis Testing under Maximum Likelihood

• The vertical distance forms the basis of the LR test.

• The Wald test is based on a comparison of the horizontal distance.

• The LM test compares the slopes of the curve at A and B.

• We know at the unrestricted MLE, L( ), the slope of the curve is zero.

• But is it “significantly steep” at ?

• This formulation of the test is usually easiest to estimate.

L( ~

)

̂

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 13

Multivariate GARCH Models

• Multivariate GARCH models are used to estimate and to forecast

covariances and correlations. The basic formulation is similar to that of the

GARCH model, but where the covariances as well as the variances are

permitted to be time-varying.

• There are 3 main classes of multivariate GARCH formulation that are widely

used: VECH, diagonal VECH and BEKK.

VECH and Diagonal VECH

• e.g. suppose that there are two variables used in the model. The conditional

covariance matrix is denoted Ht, and would be 2  2. Ht and VECH(Ht) are

  

  

t

t

t

t

h

h

h

HVECH

12

22

11

)( 

  

 

tt

tt

t hh

hh H

2221

1211

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 14

VECH and Diagonal VECH

• In the case of the VECH, the conditional variances and covariances would each depend upon lagged values of all of the variances and covariances and on lags of the squares of both error terms and their cross products.

• In matrix form, it would be written

• Writing out all of the elements gives the 3 equations as

• Such a model would be hard to estimate. The diagonal VECH is much simpler and is specified, in the 2 variable case, as follows:

• The BEKK Model uses a Quadratic form for the parameter matrices to ensure a positive definite variance / covariance matrix Ht.

112212111012

1222

2

121022

1112

2

111011













tttt

ttt

ttt

huuh

huh

huh







     111   tttt HVECHBVECHACHVECH  ttt HN ,0~1 

1123312232111312133

2

232

2

1313112

1122312222111212123

2

222

2

1212122

1121312212111112113

2

212

2

1111111













tttttttt

tttttttt

tttttttt

hbhbhbuuauauach

hbhbhbuuauauach

hbhbhbuuauauach

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 15

BEKK and Model Estimation for M-GARCH

• Neither the VECH nor the diagonal VECH ensure a positive definite variance-

covariance matrix.

• An alternative approach is the BEKK model (Engle & Kroner, 1995).

• In matrix form, the BEKK model is

• Model estimation for all classes of multivariate GARCH model is again

performed using maximum likelihood with the following LLF:

where N is the number of variables in the system (assumed 2 above),  is a

vector containing all of the parameters to be estimated, and T is the number of

observations.

BBAHAWWH tttt 111  

    

  T

t

tttt HH TN

1

1'log 2

1 2log

2 

Topic7.pdf

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 1

Topic 7

Forecasting in Financial Econometrics

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 2

• Forecasting = prediction.

• An important test of the adequacy of a model.

e.g.

- Forecasting tomorrow‟s return on a particular share

- Forecasting the price of a house given its characteristics

- Forecasting the riskiness of a portfolio over the next year

- Forecasting the volatility of bond returns

• We can distinguish two approaches:

- Econometric (structural) forecasting

- Time series forecasting

• The distinction between the two types is somewhat blurred (e.g, VARs).

Forecasting in Econometrics: An Introduction

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 3

• Expect the “forecast” of the model to be good in-sample.

• Say we have some data - e.g. monthly FTSE returns for 120 months:

1990M1 – 1999M12. We could use all of it to build the model, or keep

some observations back:

• A good test of the model since we have not used the information from

1999M1 onwards when we estimated the model parameters.

In-Sample Versus Out-of-Sample

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 4

How to produce forecasts

• Multi-step ahead versus single-step ahead forecasts

• Recursive versus rolling windows

• To understand how to construct forecasts, we need the idea of conditional

expectations:

E(yt+1  t )

• We cannot forecast a white noise process: E(ut+s  t ) = 0  s > 0.

• The two simplest forecasting “methods”

1. Assume no change : f(yt+s) = yt

2. Forecasts are the long term average f(yt+s) =

y

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 5

Models for Forecasting

• Structural models

e.g. y = X + u

To forecast y, we require the conditional expectation of its future

value:

=

But what are etc.? We could use , so

= !!

tktktt uxxy   221

   tktkttt uxxEyE    2211

   ktkt xExE   221

)( 2tx 2x

  kkt xxyE   221

y

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 6

Models for Forecasting (cont’d)

• Time Series Models

The current value of a series, yt, is modelled as a function only of its previous

values and the current value of an error term (and possibly previous values of

the error term).

• Models include:

• simple unweighted averages

• exponentially weighted averages

• ARIMA models

• Non-linear models – e.g. threshold models, GARCH, bilinear models, etc.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 7

The forecasting model typically used is of the form:

where ft,s = yt+s , s 0; ut+s = 0, s > 0

= ut+s , s  0

Forecasting with ARMA Models

 



  q

j

jstj

p

i

istist uff 11

,, 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 8

• An MA(q) only has memory of q.

e.g. say we have estimated an MA(3) model:

yt =  + 1ut-1 +  2ut-2 +  3ut-3 + ut

yt+1 =  +  1ut +  2ut-1 +  3ut-2 + ut+1

yt+2 =  +  1ut+1 +  2ut +  3ut-1 + ut+2

yt+3 =  +  1ut+2 +  2ut+1 +  3ut + ut+3

• We are at time t and we want to forecast 1,2,..., s steps ahead.

• We know yt , yt-1, ..., and ut , ut-1

Forecasting with MA Models

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 9

ft, 1 = E(yt+1  t ) = E( +  1ut +  2ut-1 +  3ut-2 + ut+1)

=  +  1ut +  2ut-1 +  3ut-2

ft, 2 = E(yt+2  t ) = E( +  1ut+1 +  2ut +  3ut-1 + ut+2)

=  +  2ut +  3ut-1

ft, 3 = E(yt+3  t ) = E( +  1ut+2 +  2ut+1 +  3ut + ut+3)

=  +  3ut

ft, 4 = E(yt+4  t ) = 

ft, s = E(yt+s  t ) =   s  4

Forecasting with MA Models (cont’d)

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 10

• Say we have estimated an AR(2)

yt =  + 1yt-1 +  2yt-2 + ut

yt+1 =  +  1yt +  2yt-1 + ut+1

yt+2 =  +  1yt+1 +  2yt + ut+2

yt+3 =  +  1yt+2 +  2yt+1 + ut+3

ft, 1 = E(yt+1  t ) = E( +  1yt +  2yt-1 + ut+1)

=  +  1E(yt) +  2E(yt-1)

=  +  1yt +  2yt-1

ft, 2 = E(yt+2  t ) = E( +  1yt+1 +  2yt + ut+2)

=  +  1E(yt+1) +  2E(yt)

=  +  1 ft, 1 +  2yt

Forecasting with AR Models

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 11

ft, 3 = E(yt+3  t ) = E( +  1yt+2 +  2yt+1 + ut+3)

=  +  1E(yt+2) +  2E(yt+1)

=  +  1 ft, 2 +  2 ft, 1

• We can see immediately that

ft, 4 =  +  1 ft, 3 +  2 ft, 2 etc., so

ft, s =  +  1 ft, s-1 +  2 ft, s-2

• Can easily generate ARMA(p,q) forecasts in the same way.

Forecasting with AR Models (cont’d)

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 12

•For example, say we predict that tomorrow‟s return on the FTSE will be 0.2, but

the outcome is actually -0.4. Is this accurate? Define ft,s as the forecast made at time t for s steps ahead (i.e. the forecast made for time t+s), and yt+s as the realised value of y at time t+s.

• Some of the most popular criteria for assessing the accuracy of time series forecasting techniques are:

MAE is given by

Mean absolute percentage error:

How can we test whether a forecast is accurate or not?

2

,

1

)( 1

stst

N

t

fy N

MSE  

stst

N

t

fy N

MAE ,

1

1  

st

stst N

t y

fy

N MAPE

  

,

1

1 100

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 13

• It has, however, also recently been shown (Gerlow et al., 1993) that the

accuracy of forecasts according to traditional statistical criteria are not

related to trading profitability.

• A measure more closely correlated with profitability:

% correct sign predictions =

where zt+s = 1 if (xt+s . ft,s ) > 0

zt+s = 0 otherwise

How can we test whether a forecast is accurate or not?

(cont’d)

 

N

t stz

N 1

1

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 14

• Given the following forecast and actual values, calculate the MSE, MAE and percentage of correct sign predictions:

• MSE = 0.079, MAE = 0.180, % of correct sign predictions = 40

Forecast Evaluation Example

Steps Ahead Forecast Actual

1 0.20 -0.40

2 0.15 0.20

3 0.10 0.10

4 0.06 -0.10

5 0.04 -0.05

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 15

What factors are likely to lead to a

good forecasting model?

• “signal” versus “noise”

• “data mining” issues

• simple versus complex models

• financial or economic theory

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 16

Statistical Versus Economic or

Financial loss functions

• Statistical evaluation metrics may not be appropriate.

• How well does the forecast perform in doing the job we wanted it for?

Limits of forecasting: What can and cannot be forecast?

• All statistical forecasting models are essentially extrapolative

• Forecasting models are prone to break down around turning points

• Series subject to structural changes or regime shifts cannot be forecast

• Predictive accuracy usually declines with forecasting horizon

• Forecasting is not a substitute for judgement

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 17

Back to the original question: why forecast?

• Why not use “experts” to make judgemental forecasts?

• Judgemental forecasts bring a different set of problems:

e.g., psychologists have found that expert judgements are prone to the following biases:

– over-confidence

– inconsistency

– recency

– anchoring

– illusory patterns

– “group-think”.

• The Usually Optimal Approach

To use a statistical forecasting model built on solid theoretical foundations supplemented by expert judgements and interpretation.

Forecasting with Non-Stationary Variables

• An ECM model can be used to produce and evaluate

forecasts when variables exhibit non-stationarity

• For an illustration we return to the example of the lead-lag

relationship between spot and futures prices

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 18

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 19

An Example of a Model for Non-stationary

Variables: Lead-Lag Relationships between Spot

and Futures Prices

Background

• We expect changes in the spot price of a financial asset and its corresponding futures price to be perfectly contemporaneously correlated and not to be cross-autocorrelated.

i.e. expect Corr(ln(Ft),ln(St))  1

Corr(ln(Ft),ln(St-k))  0  k

Corr(ln(Ft-j),ln(St))  0  j

• We can test this idea by modelling the lead-lag relationship between the two.

• We will consider two papers Tse(1995) and Brooks et al (2001).

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 20

Futures & Spot Data

• Tse (1995): 1055 daily observations on NSA stock index and stock

index futures values from December 1988 - April 1993.

• Brooks et al (2001): 13,035 10-minutely observations on the FTSE

100 stock index and stock index futures prices for all trading days in

the period June 1996 – 1997.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 21

Methodology

• The fair futures price is given by

where Ft * is the fair futures price, St is the spot price, r is a

continuously compounded risk-free rate of interest, d is the

continuously compounded yield in terms of dividends derived from the

stock index until the futures contract matures, and (T-t) is the time to

maturity of the futures contract. Taking logarithms of both sides of

equation above gives

• First, test ft and st for nonstationarity.

t *

t (r-d)(T-t)F = S e

t)-d)(T-(r s f tt *

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 22

Dickey-Fuller Tests on Log-Prices and Returns for

High Frequency FTSE Data

Futures Spot

Dickey-Fuller Statistics

for Log-Price Data

-0.1329 -0.7335

Dickey Fuller Statistics

for Returns Data

-84.9968 -114.1803

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 23

Cointegration Test Regression and Test on Residuals

• Conclusion: log Ft and log St are not stationary, but log Ft and log St are stationary.

• But a model containing only first differences has no long run relationship.

• Solution is to see if there exists a cointegrating relationship between ft and st which would mean that we can validly include levels terms in this framework.

• Potential cointegrating regression:

where zt is a disturbance term.

• Estimate the regression, collect the residuals, , and test whether they are stationary.

zt

ttt zfs  10 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 24

Estimated Equation and Test for Cointegration for

High Frequency FTSE Data

Cointegrating Regression

Coefficient  0

 1

Estimated Value

0.1345

0.9834

DF Test on residuals tẑ

Test Statistic

-14.7303

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 25

Conclusions from Unit Root and Cointegration Tests

• Conclusion: are stationary and therefore we have a cointegrating

relationship between log Ft and log St.

• Final stage in Engle-Granger 2-step method is to use the first stage

residuals, as the equilibrium correction term in the general equation.

• The overall model is

zt

zt

ttttt vFSzS   111110 lnlnˆln 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 26

Estimated Error Correction Model for

High Frequency FTSE Data

Look at the signs and significances of the coefficients:

• is positive and highly significant

• is positive and highly significant

• is negative and highly significant

Coefficient Estimated Value t-ratio 0

9.6713E-06 1.6083

 -8.3388E-01 -5.1298

1 0.1799 19.2886

1 0.1312 20.4946

1̂

1̂



„Introductory Econometrics for Finance‟ © Chris Brooks 2002 27

Forecasting High Frequency FTSE Returns

• Is it possible to use the error correction model to produce superior

forecasts to other models?

Comparison of Out of Sample Forecasting Accuracy

ECM ECM-COC ARIMA VAR

RMSE 0.0004382 0.0004350 0.0004531 0.0004510

MAE 0.4259 0.4255 0.4382 0.4378

% Correct

Direction

67.69% 68.75% 64.36% 66.80%

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 28

Can Profitable Trading Rules be Derived from the

ECM-COC Forecasts?

• The trading strategy involves analysing the forecast for the spot return, and

incorporating the decision dictated by the trading rules described below. It is assumed

that the original investment is £1000, and if the holding in the stock index is zero, the

investment earns the risk free rate.

– Liquid Trading Strategy - making a round trip trade (i.e. a purchase and sale of

the FTSE100 stocks) every ten minutes that the return is predicted to be positive

by the model.

– Buy-&-Hold while Forecast Positive Strategy - allows the trader to continue

holding the index if the return at the next predicted investment period is positive.

– Filter Strategy: Better Predicted Return Than Average - involves purchasing the

index only if the predicted returns are greater than the average positive return.

– Filter Strategy: Better Predicted Return Than First Decile - only the returns

predicted to be in the top 10% of all returns are traded on

– Filter Strategy: High Arbitrary Cut Off - An arbitrary filter of 0.0075% is

imposed,

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 29

Trading Strategy Terminal Wealth

( £ )

Return ( % ) {Annualised}

Terminal Wealth (£)

with slippage

Return ( % ) {Annualised}

with slippage

Number

of trades

Passive

Investment

1040.92 4.09

{49.08}

1040.92 4.09

{49.08}

1

Liquid Trading 1156.21 15.62

{187.44}

1056.38 5.64

{67.68}

583

Buy-&-Hold while

Forecast Positive

1156.21 15.62

{187.44}

1055.77 5.58

{66.96}

383

Filter I 1144.51 14.45 {173.40}

1123.57 12.36 {148.32}

135

Filter II 1100.01 10.00 {120.00}

1046.17 4.62 {55.44}

65

Filter III 1019.82 1.98 {23.76}

1003.23 0.32 {3.84}

8

Spot Trading Strategy Results for Error Correction

Model Incorporating the Cost of Carry

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 30

Conclusions

• The futures market “leads” the spot market because:

• the stock index is not a single entity, so

• some components of the index are infrequently traded

• it is more expensive to transact in the spot market

• stock market indices are only recalculated every minute

• Spot & futures markets do indeed have a long run relationship.

• Since it appears impossible to profit from lead/lag relationships, their

existence is entirely consistent with the absence of arbitrage

opportunities and in accordance with modern definitions of the

efficient markets hypothesis.

Forecasting in Non-Linear Models

• GARCH models can be used to forecast (conditional) variance

• Interpretation: volatility forecasts

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 31

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 32

Forecasting Variances using GARCH Models

• Producing conditional variance forecasts from GARCH models uses a very similar approach to producing forecasts from ARMA models.

• It is again an exercise in iterating with the conditional expectations operator.

• Consider the following GARCH(1,1) model:

, ut  N(0,t 2),

• What is needed is to generate are forecasts of T+1 2 T, T+2

2 T, ..., T+s

2 T where T denotes all information available up to and including observation T.

• Adding one to each of the time subscripts of the above conditional variance equation, and then two, and then three would yield the following equations

T+1 2 = 0 + 1 +T

2 , T+2 2 = 0 + 1 +T+1

2 , T+3 2 = 0 + 1 +T+2

2

tt uy   2

1

2

110

2

  ttt u 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 33

Forecasting Variances

using GARCH Models (Cont’d)

• Let be the one step ahead forecast for 2 made at time T. This is

easy to calculate since, at time T, the values of all the terms on the

RHS are known.

• would be obtained by taking the conditional expectation of the

first equation at the bottom of slide 36:

• Given, how is , the 2-step ahead forecast for 2 made at time T,

calculated? Taking the conditional expectation of the second equation

at the bottom of slide 36:

= 0 + 1E(  T) +

• where E(  T) is the expectation, made at time T, of , which is

the squared disturbance term.

2

,1

f

T

2

,1

f

T

2

,1

f

T = 0 + 1 2

Tu +T 2

2

,1

f

T 2

,2

f

T

2

,2

f

T 2

1Tu 2

,1

f

T 2

1Tu 2

1Tu

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 34

Forecasting Variances

using GARCH Models (Cont’d)

• We can write

E(uT+1 2  t) = T+1

2

• But T+1 2 is not known at time T, so it is replaced with the forecast for

it, , so that the 2-step ahead forecast is given by

= 0 + 1 +

= 0 + (1+)

• By similar arguments, the 3-step ahead forecast will be given by

= ET(0 + 1 + T+2 2)

= 0 + (1+)

= 0 + (1+)[ 0 + (1+) ]

= 0 + 0(1+) + (1+)2

• Any s-step ahead forecast (s  2) would be produced by

2

,1

f

T 2

,2

f

T 2

,1

f

T 2

,1

f

T 2

,2

f

T 2

,1

f

T

2

,3

f

T 2

,2

f

T 2

,1

f

T 2

,1

f

T

f

T

s s

i

if

Ts hh ,1

1

1

1

1

1

10, )()(  

   

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 35

What Use Are Volatility Forecasts?

1. Option pricing

C = f(S, X, 2, T, rf)

2. Conditional betas

3. Dynamic hedge ratios

The Hedge Ratio - the size of the futures position to the size of the

underlying exposure, i.e. the number of futures contracts to buy or sell per

unit of the spot good.

 

 i t

im t

m t

, ,

,

 2

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 36

What Use Are Volatility Forecasts? (Cont’d)

• What is the optimal value of the hedge ratio?

• Assuming that the objective of hedging is to minimise the variance of the hedged portfolio, the optimal hedge ratio will be given by

where h = hedge ratio

p = correlation coefficient between change in spot price (S) and change in futures price (F)

S = standard deviation of S

F = standard deviation of F

• What if the standard deviations and correlation are changing over time?

Use

h p s

F

 

tF

ts

tt ph ,

,

 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 37

An Example of the Application of GARCH Models

- Day & Lewis (1992)

• Purpose

• To consider the out of sample forecasting performance of GARCH and EGARCH Models for predicting stock index volatility.

• Implied volatility is the markets expectation of the “average” level of volatility of an option:

• Which is better, GARCH or implied volatility?

• Data

• Weekly closing prices (Wednesday to Wednesday, and Friday to Friday) for the S&P100 Index option and the underlying 11 March 83 - 31 Dec. 89

• Implied volatility is calculated using a non-linear iterative procedure.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 38

The Models

• The “Base” Models

For the conditional mean

(1)

And for the variance (2)

or (3)

where

RMt denotes the return on the market portfolio

RFt denotes the risk-free rate

ht denotes the conditional variance from the GARCH-type models while t

2 denotes the implied variance from option prices.

ttFtMt uhRR  10 

11

2

110   ttt huh 

) 2

()ln()ln(

2/1

1

1

1

1

1110

 

 

  

  

 

 

 t

t

t

t

tt h

u

h

u hh

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 39

The Models (cont’d)

• Add in a lagged value of the implied volatility parameter to equations (2) and (3).

(2) becomes

(4)

and (3) becomes

(5)

• We are interested in testing H0 :  = 0 in (4) or (5).

• Also, we want to test H0 : 1 = 0 and 1 = 0 in (4),

• and H0 : 1 = 0 and 1 = 0 and  = 0 and  = 0 in (5).

2

111

2

110   tttt huh 

)ln() 2

()ln()ln( 2

1

2/1

1

1

1

1

1110 

   

 

  

  

  t

t

t

t

t

tt h

u

h

u hh 

 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 40

The Models (cont’d)

• If this second set of restrictions holds, then (4) & (5) collapse to

(4‟)

• and (3) becomes

(5‟)

• We can test all of these restrictions using a likelihood ratio test.

2

10

2

 tth 

)ln()ln( 2

10

2

 tth 

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 41

In-sample Likelihood Ratio Test Results:

GARCH Versus Implied Volatility

ttFtMt uhRR  10  (8.78)

11

2

110   ttt huh  (8.79)

2

111

2

110   tttt huh  (8.81)

2

10

2

 tth  (8.81)

Equation for Variance

specification

0 1 010-4 1 1  Log-L 2

(8.79) 0.0072

(0.005)

0.071

(0.01)

5.428

(1.65)

0.093

(0.84)

0.854

(8.17)

- 767.321 17.77

(8.81) 0.0015 (0.028)

0.043 (0.02)

2.065 (2.98)

0.266 (1.17)

-0.068 (-0.59)

0.318 (3.00)

776.204 -

(8.81) 0.0056 (0.001)

-0.184 (-0.001)

0.993 (1.50)

- - 0.581 (2.94)

764.394 23.62

Notes: t-ratios in parentheses, Log-L denotes the maximised value of the log-likelihood function in

each case. 2 denotes the value of the test statistic, which follows a 2

(1) in the case of (8.81) restricted

to (8.79), and a 2 (2) in the case of (8.81) restricted to (8.81). Source: Day and Lewis (1992).

Reprinted with the permission of Elsevier Science.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 42

In-sample Likelihood Ratio Test Results:

EGARCH Versus Implied Volatility

ttFtMt uhRR  10  (8.78)

) 2

()ln()ln(

2/1

1

1

1

1

1110

 

 

  

  

 

 

 t

t

t

t tt

h

u

h

u hh (8.80)

)ln() 2

()ln()ln( 2

1

2/1

1

1

1

1

1110 

   

 

  

  

  t

t

t

t

t

tt h

u

h

u hh 

  (8.82)

)ln()ln( 2

10

2

 tth  (8.82)

Equation for

Variance specification

0 1 010-4 1    Log-L 2

(c) -0.0026 (-0.03)

0.094 (0.25)

-3.62 (-2.90)

0.529 (3.26)

-0.273 (-4.13)

0.357 (3.17)

- 776.436 8.09

(e) 0.0035 (0.56)

-0.076 (-0.24)

-2.28 (-1.82)

0.373 (1.48)

-0.282 (-4.34)

0.210 (1.89)

0.351 (1.82)

780.480 -

(e) 0.0047 (0.71)

-0.139 (-0.43)

-2.76 (-2.30)

- - - 0.667 (4.01)

765.034 30.89

Notes: t-ratios in parentheses, Log-L denotes the maximised value of the log-likelihood function in

each case. 2 denotes the value of the test statistic, which follows a 2

(1) in the case of (8.82) restricted

to (8.80), and a 2 (2) in the case of (8.82) restricted to (8.82). Source: Day and Lewis (1992).

Reprinted with the permission of Elsevier Science.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 43

Conclusions for In-sample Model Comparisons &

Out-of-Sample Procedure

• IV has extra incremental power for modelling stock volatility beyond GARCH.

• But the models do not represent a true test of the predictive ability of IV.

• So the authors conduct an out of sample forecasting test.

• There are 729 data points. They use the first 410 to estimate the models, and then make a 1-step ahead forecast of the following week‟s volatility.

• Then they roll the sample forward one observation at a time, constructing a new one step ahead forecast at each step.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 44

Out-of-Sample Forecast Evaluation

• They evaluate the forecasts in two ways:

• The first is by regressing the realised volatility series on the forecasts plus a constant:

(7)

where is the “actual” value of volatility, and is the value forecasted for it during period t.

• Perfectly accurate forecasts imply b0 = 0 and b1 = 1.

• But what is the “true” value of volatility at time t ?

Day & Lewis use 2 measures

1. The square of the weekly return on the index, which they call SR.

2. The variance of the week‟s daily returns multiplied by the number of trading days in that week.

  t ft tb b   1 2

0 1 2

1

t1 2

 ft 2

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 45

Out-of Sample Model Comparisons

1

2

10

2

1   tftt bb  (8.83)

Forecasting Model Proxy for ex

post volatility

b0 b1 R2

Historic SR 0.0004 (5.60)

0.129 (21.18)

0.094

Historic WV 0.0005 (2.90)

0.154 (7.58)

0.024

GARCH SR 0.0002 (1.02)

0.671 (2.10)

0.039

GARCH WV 0.0002 (1.07)

1.074 (3.34)

0.018

EGARCH SR 0.0000 (0.05)

1.075 (2.06)

0.022

EGARCH WV -0.0001 (-0.48)

1.529 (2.58)

0.008

Implied Volatility SR 0.0022 (2.22)

0.357 (1.82)

0.037

Implied Volatility WV 0.0005

(0.389)

0.718

(1.95)

0.026

Notes: Historic refers to the use of a simple historical average of the squared returns to forecast

volatility; t-ratios in parentheses; SR and WV refer to the square of the weekly return on the S&P 100,

and the variance of the week‟s daily returns multiplied by the number of trading days in that week,

respectively. Source: Day and Lewis (1992). Reprinted with the permission of Elsevier Science.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 46

Encompassing Test Results: Do the IV Forecasts

Encompass those of the GARCH Models?

1

2

4

2

3

2

2

2

10

2

1   tHtEtGtItt bbbbb  (8.86)

Forecast comparison b0 b1 b2 b3 b4 R2

Implied vs. GARCH

-0.00010 (-0.09)

0.601 (1.03)

0.298 (0.42)

- - 0.027

Implied vs. GARCH

vs. Historical

0.00018

(1.15)

0.632

(1.02)

-0.243

(-0.28)

- 0.123

(7.01)

0.038

Implied vs. EGARCH

-0.00001 (-0.07)

0.695 (1.62)

- 0.176 (0.27)

- 0.026

Implied vs. EGARCH vs. Historical

0.00026 (1.37)

0.590 (1.45)

-0.374 (-0.57)

- 0.118 (7.74)

0.038

GARCH vs. EGARCH

0.00005 (0.37)

- 1.070 (2.78)

-0.001 (-0.00)

- 0.018

Notes: t-ratios in parentheses; the ex post measure used in this table is the variance of the week‟s daily

returns multiplied by the number of trading days in that week. Source: Day and Lewis (1992).

Reprinted with the permission of Elsevier Science.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 47

Conclusions of Paper

• Within sample results suggest that IV contains extra information not

contained in the GARCH / EGARCH specifications.

• Out of sample results suggest that nothing can accurately predict

volatility!

• The next example looks at a multivariate GARCH model.

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 48

An Example: Estimating a Time-Varying Hedge Ratio

for FTSE Stock Index Returns

(Brooks, Henry and Persand, 2002).

• Data comprises 3580 daily observations on the FTSE 100 stock index and

stock index futures contract spanning the period 1 January 1985 - 9 April 1999.

• Several competing models for determining the optimal hedge ratio are

constructed. Define the hedge ratio as .

– No hedge (=0)

– Naïve hedge (=1)

– Multivariate GARCH hedges:

• Symmetric BEKK

• Asymmetric BEKK

In both cases, estimating the OHR involves forming a 1-step ahead

forecast and computing

t

tF

tCF

t h

h OHR 

1,

1,

1

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 49

OHR Results

In Sample

Unhedged

 = 0

Naïve Hedge

 = 1

Symmetric Time

Varying

Hedge

tF

tFC

t h

h

,

, 

Asymmetric

Time Varying

Hedge

tF

tFC

t h

h

,

, 

Return 0.0389 {2.3713}

-0.0003 {-0.0351}

0.0061 {0.9562}

0.0060 {0.9580}

Variance 0.8286 0.1718 0.1240 0.1211

Out of Sample

Unhedged

 = 0

Naïve Hedge

 = 1

Symmetric Time

Varying Hedge

tF

tFC

t h

h

,

, 

Asymmetric

Time Varying Hedge

tF

tFC

t h

h

,

, 

Return 0.0819

{1.4958}

-0.0004

{0.0216}

0.0120

{0.7761}

0.0140

{0.9083} Variance 1.4972 0.1696 0.1186 0.1188

„Introductory Econometrics for Finance‟ © Chris Brooks 2002 50

Plot of the OHR from Multivariate GARCH

Conclusions

- OHR is time-varying and less

than 1

- M-GARCH OHR provides a

better hedge, both in-sample

and out-of-sample.

- No role in calculating OHR for

asymmetries

Symmetric BEKK

Asymmetric BEKK

Time Varying Hedge Ratios

500 1000 1500 2000 2500 3000 0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

FMBF_Assessment_201314.pdf

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Financial Modelling and Business Forecasting 2013/14 Masters Programmes

SUMMATIVE ASSIGNMENT

Obtain data on bilateral exchange rates and consumer price index for three

countries: France, Belgium and Germany. The frequency of the data should be

monthly and should span a period post-Bretton-Woods system and before

introduction of a single currency, that is, from 1973 to 1990. Take the natural log of

the variables and split the sample period into two parts: one part containing all of the

observations excluding the last 10 observations and the other part containing the last

10 observations. The larger sub-sample is to be used to answer questions (1) to (4)

and the smaller sample is to be used in the forecasting question (question (5)).

Analyse the time-series properties of your series as follows;

(1) Identify the summary statistics which describe the statistical properties of each series and provide a rationale for your choice. Calculate the chosen summary statistics and analyse briefly the results obtained.

(10 marks)

(2) Test for the presence of unit roots in all series. Explain carefully the testing procedure used.

(10 marks)

(3) Explain what you can do to test the hypothesis of the long-run Purchasing Power Parity (PPP) for a given pair of countries, with the reference to the appropriate theoretical and empirical literature. Find if there is evidence in your data in support of the long-run PPP hypothesis for each pair of countries.

(30 marks)

(4) Identify and estimate a suitable autoregressive (AR) model for any one of the exchange rate series. Test for ARCH effects in the chosen series. Re-estimate your model using an appropriate GARCH model for the conditional variance. Comment succinctly on the usefulness of your GARCH model in finance.

(25 marks)

(5) Forecast the mean and the variance of the model obtained in question (4) for the last 15 observations. Re-estimate your model using an asymmetric GARCH model. Critically compare the properties of the two models in the context of their usefulness in finance.

(25 marks)

Financial Modelling and Business Forecasting 2013/14 Masters Programmes

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Guidance:

1. You will be marked according to how well you conduct the econometric

exercises, estimations, forecasts and your critical evaluation including a critical

comparison of your results with those provided in the literature.

2. Include in the main text any tables or graphs necessary to understand your

explanations and results.

3. Include, either in the main text or in an annex, all the computer printouts used.

Overall word limit, 2,500 words maximum.

YOU ARE NOT REQUIRED TO SUBMIT A PAPER COPY OF THIS ASSIGNMENT

TO THE MASTERS OFFICE.

YOU ARE REQUIRED TO SUBMIT AN ELECTRONIC COPY TO DUO NO LATER

THAN 5.00PM ON 2 MAY 2014

YOU ARE ALSO REQUIRED TO EMAIL A COPY OF YOUR DATA TO

[email protected] BY 5.00PM 2 MAY 2014

Overall word limit, 2500 words maximum.

The word count should:

 Include all the text, including title, preface, introduction, in-text citations, quotations,

footnotes and any other item not specifically excluded below.

 Exclude diagrams, tables (including tables/lists of contents and figures), equations,

executive summary/abstract, acknowledgements, declaration, bibliography/list of

references and appendices. However, it is not appropriate to use diagrams or tables

merely as a way of circumventing the word limit. If a student uses a table or figure as

a means of presenting his/her own words, then this is included in the word count.

Examiners will stop reading once the word limit has been reached, and work beyond this

point will not be assessed. Checks of word counts will be carried out on submitted work,

including any assignments or dissertations/business projects that appear to be clearly over-

length. Checks may take place manually and/or with the aid of the word count provided via

an electronic submission. Where a student has intentionally misrepresented their word

count, the School may treat this as an offence under Section IV of the General Regulations

of the University. Extreme cases may be viewed as dishonest practice under Section IV, 5

(a) (x) of the General Regulations.

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Very occasionally it may be appropriate to present, in an appendix, material which does not

properly belong in the main body of the assessment but which some students wish to

provide for the sake of completeness. Any appendices will not have a role in the assessment

– examiners are under no obligation to read appendices and they do not form part of the

word count. Material that students wish to be assessed should always be included in the

main body of the text.

MARKING GUIDELINES

Performance in the summative assessment for this module is judged against the following

criteria:

 Relevance to question

 Organisation, structure and presentation

 Depth of understanding

 Analysis and discussion

 Use of sources and referencing

 Overall conclusions

Students are strongly advised to use Arial font size 11 for their assignments and to print

double sided.

Assignments must be typed or word-processed on A4 paper using 1.5 or double spacing and

with margins of 2-3 cm. Pages should be numbered and stapled together in the top left hand

corner. The word count should include all the text (plus endnotes and footnotes), but exclude

diagrams, tables, bibliography, references and appendices. Guidance on referencing can be

found in your year handbook.

You are required to submit an electronic copy of your assignment on DUO which will be put

through the plagiarism detection service.

The electronic version of the assignment which you submit on-line should EXCLUDE all

appendices and extracts from the companies’ financial statements.

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PLAGIARISM and COLLUSION

Students suspected of plagiarism, either of published work or work from unpublished

sources, including the work of other students, or of collusion will be dealt with according to

Business School and University guidelines.

You are required to submit an electronic copy of your assignment on DUO which will be put

through the plagiarism detection service. The deadline for your electronic copy is

5.00pm on 2 May 2014

FMBF_Seminar1_Answers.doc