microeconomic
titanicdicar
MiCh14FirmsinCompetitiveMarkets.pptxFirms in
Competitive Markets
CHAPTER
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PowerPoint Slides prepared by:
V. Andreea CHIRITESCU
Eastern Illinois University
N. GREGORY MANKIW PRINCIPLES OF MICROECONOMICS Eight Edition
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What is a Competitive Market?
Competitive market
Perfectly competitive market
Market with many buyers and sellers
Trading identical products
Each buyer and seller is a price taker
Firms can freely enter or exit the market
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What is a Competitive Market?
Firm in a competitive market
Tries to maximize profit
Profit
Total revenue minus total cost
Total revenue, TR = P ˣ Q
Price times quantity
Proportional to the amount of output
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What is a Competitive Market?
Average revenue, AR = TR / Q
Total revenue divided by the quantity sold
Marginal revenue, MR = ∆TR / ∆Q
Change in total revenue from an additional unit sold
For competitive firms
AR = P
MR = P
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Table 1 Total, Average, and Marginal Revenue for a Competitive Firm
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Profit Maximization
Maximize profit
Produce quantity where total revenue minus total cost is greatest
Compare marginal revenue with marginal cost
If MR > MC: increase production
If MR < MC: decrease production
Maximize profit where MR = MC
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Table 2 Profit Maximization: A Numerical Example
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Profit Maximization
The marginal-cost curve and the firm’s supply decision
MC curve is upward sloping
ATC curve is U-shaped
MC curve crosses the ATC curve at the minimum of ATC curve
The price line is horizontal: P = AR = MR
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Figure 1 Profit Maximization for a Competitive Firm
This figure shows the marginal-cost curve (MC), the average-total-cost curve (ATC), and the average-variable-cost curve (AVC). It also shows the market price (P), which for a competitive firm equals both marginal revenue (MR) and average revenue (AR).
At the quantity Q1, MR1 > MC1, so raising production increases profit.
At the quantity Q2, MC2 > MR2, so reducing production increases profit.
The profit-maximizing quantity QMAX is found where the horizontal line representing the price intersects the marginal-cost curve.
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Costs
and
Revenue
Quantity
0
ATC
AVC
P=AR=MR
P=MR1=MR2
MC
MC1
MC2
Q2
Q1
QMAX
The firm maximizes profit by producing the quantity at which marginal cost equals marginal revenue.
Profit Maximization
Rules for profit maximization:
If MR > MC, firm should increase output
If MC > MR, firm should decrease output
If MR = MC, profit-maximizing level of output
Marginal-cost curve
Determines the quantity of the good the firm is willing to supply at any price
Is the supply curve
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Figure 2 Marginal Cost as the Competitive Firm’s Supply Curve
An increase in the price from P1 to P2 leads to an increase in the firm’s profit-maximizing quantity from Q1 to Q2. Because the marginal-cost curve shows the quantity supplied by the firm at any given price, it is the firm’s supply curve.
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Price
Quantity
0
ATC
AVC
MC
P1
P2
Q2
Q1
Profit Maximization
Shutdown
Short-run decision not to produce anything
During a specific period of time
Because of current market conditions
Firm still has to pay fixed costs
Exit
Long-run decision to leave the market
Firm doesn’t have to pay any costs
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Profit Maximization
The firm’s short-run decision to shut down
TR = total revenue
VC = variable costs
Firm’s decision:
Shut down if TR < VC (or P < AVC)
Competitive firm’s short-run supply curve
The portion of its marginal-cost curve
That lies above average variable cost
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Figure 3 The Competitive Firm’s Short-Run Supply Curve
In the short run, the competitive firm’s supply curve is its marginal-cost curve (MC) above average variable cost (AVC). If the price falls below average variable cost, the firm is better off shutting down temporarily.
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Costs
Quantity
0
ATC
MC
AVC
1. In the short run, the firm produces on the MC curve if P>AVC,...
2. ...but
shuts down
if P<AVC.
Profit Maximization
Sunk cost
A cost that has already been committed and cannot be recovered
Should be ignored when making decisions
“Don’t cry over spilt milk”
“Let bygones be bygones”
In the short run, fixed costs are sunk costs
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Near-empty restaurants & off-season miniature golf
Restaurant – stay open for lunch?
Fixed costs: not relevant; are sunk costs in short run
Variable costs, VC: relevant
Shut down if revenue from lunch < VC
Stay open if revenue from lunch > VC
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Staying open can be profitable, even with many tables empty.
Near-empty restaurants & off-season miniature golf
Operator of a miniature-golf course
Ignore fixed costs
Shut down if
Revenue < variable costs
Stay open if
Revenue > variable costs
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Profit Maximization
Firm’s long-run decision
Exit the market if
Total revenue < total costs; TR < TC (same as: P < ATC)
Enter the market if
Total revenue > total costs; TR > TC (same as: P > ATC)
Competitive firm’s long-run supply curve
The portion of its marginal-cost curve that lies above average total cost
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Figure 4 The Competitive Firm’s Long-Run Supply Curve
In the long run, the competitive firm’s supply curve is its marginal-cost curve (MC) above average total cost (ATC). If the price falls below average total cost, the firm is better off exiting the market.
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Costs
Quantity
0
MC
1. In the long run, the firm produces on the MC curve if P>ATC,...
2. ...but exits if P<ATC
ATC
Profit Maximization
Measuring profit
If P > ATC
Profit = TR – TC = (P – ATC) ˣ Q
If P < ATC
Loss = TC - TR = (ATC – P) ˣ Q
= Negative profit
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Figure 5 Profit as the Area between Price and Average Total Cost
The area of the shaded box between price and average total cost represents the firm’s profit. The height of this box is price minus average total cost (P – ATC), and the width of the box is the quantity of output (Q). In panel (a), price is above average total cost, so the firm has positive profit. In panel (b), price is less than average total cost, so the firm incurs a loss.
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Price
Quantity
0
(a) A firm with profits
Profit
MC
ATC
P=AR=MR
P
Q
(profit-maximizing quantity)
ATC
Price
Quantity
0
(b) A firm with losses
Loss
MC
ATC
P=AR=MR
P
Q
(loss-minimizing quantity)
ATC
Supply Curve
Short run: market supply with a fixed number of firms
Short run: number of firms is fixed
Each firm supplies quantity where P = MC
For P > AVC: supply curve is MC curve
Market supply
Add up quantity supplied by each firm
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Figure 6 Short-Run Market Supply
In the short run, the number of firms in the market is fixed. As a result, the market supply curve, shown in panel (b), reflects the individual firms’ marginal-cost curves, shown in panel (a). Here, in a market of 1,000 firms, the quantity of output supplied to the market is 1,000 times the quantity supplied by each firm
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Price
Quantity
(firm)
0
(a) Individual firm supply
MC
100
$2.00
Price
Quantity
(market)
0
(b) Market supply
200
1.00
Supply
100,000
$2.00
200,000
1.00
Supply Curve
Long run
Firms can enter and exit the market
If P > ATC, firms make positive profit
New firms enter the market
If P < ATC, firms make negative profit
Firms exit the market
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Supply Curve
Long run
Process of entry and exit ends when
Firms still in market make zero economic profit (P = ATC)
Because MC = ATC: Efficient scale
Long run supply curve is perfectly elastic
Horizontal at minimum ATC
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Figure 7 Long-Run Market Supply
In the long run, firms will enter or exit the market until profit is driven to zero. As a result, price equals the minimum of average total cost, as shown in panel (a). The number of firms adjusts to ensure that all demand is satisfied at this price. The long-run market supply curve is horizontal at this price, as shown in panel (b).
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Price
Quantity
(firm)
0
(a) Firm’s Zero-Profit Condition
MC
ATC
Price
Quantity
(market)
0
(b) Market supply
P=
minimum
ATC
Supply
Supply Curve
Why do competitive firms stay in business if they make zero profit?
Profit = total revenue – total cost
Total cost includes all opportunity costs
Zero-profit equilibrium
Economic profit is zero
Accounting profit is positive
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“We’re a nonprofit organization - we don’t intend to be, but we are!”
Supply Curve
Market in long run equilibrium
P = minimum ATC
Zero economic profit
Increase in demand
Demand curve shifts outward
Short run
Higher quantity
Higher price: P > ATC, positive economic profit
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Supply Curve
Positive economic profit in short run
Long run – firms enter the market
Short run supply curve – shifts right
Price – decreases back to minimum ATC
Quantity – increases
Because there are more firms in the market
Efficient scale
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Figure 8 An Increase in Demand in the Short Run and Long Run (a)
The market starts in a long-run equilibrium, shown as point A in panel (a). In this equilibrium, each firm makes zero profit, and the price equals the minimum average total cost.
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Price
Price
Quantity
(market)
0
Market
Quantity
(firm)
0
Firm
ATC
MC
(a) Initial Condition
Short-run supply, S1
Demand, D1
Q1
P1
Long-run
supply
P1
A
1. A market begins in
long-run equilibrium…
2. …with the firm
earning zero profit.
Figure 8 An Increase in Demand in the Short Run and Long Run (b)
Panel (b) shows what happens in the short run when demand rises from D1 to D2. The equilibrium goes from point A to point B, price rises from P1 to P2, and the quantity sold in the market rises from Q1 to Q2. Because price now exceeds average total cost, each firm now makes a profit, which over time encourages new firms to enter the market.
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Price
Price
Quantity
(market)
0
Market
Quantity
(firm)
0
Firm
(b) Short-Run Response
S1
D1
Q1
P1
Long-run
supply
P1
A
3. But then an increase in demand raises the price…
4. …leading to
short-run profits.
D2
B
Q2
P2
P2
MC
ATC
Figure 8 An Increase in Demand in the Short Run and Long Run (c)
This entry shifts the short-run supply curve to the right from S1 to S2, as shown in panel (c). In the new long-run equilibrium, point C, price has returned to P1 but the quantity sold has increased to Q3. Profits are again zero, and price is back to the minimum of average total cost, but the market has more firms to satisfy the greater demand.
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Price
Price
Quantity
(market)
0
Market
Quantity
(firm)
0
Firm
(c) Long-Run Response
S1
D1
Q1
A
D2
B
Q2
P2
MC
ATC
5. When profits induce entry, supply increases and the price falls,…
6. …restoring long-run equilibrium.
S2
C
Q3
P1
P1
Long-run
supply
Supply Curve
Long-run supply curve might slope upward
Some resource used in production may be available only in limited quantities
Increase in quantity supplied – increase in costs – increase in price
Firms may have different costs
Some firms earn profit even in the long run
Long-run supply curve
More elastic than short-run supply curve
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