(Econ) 4 questions.

>> All right, in this working   with diagram's feature we're going to look at and exhibit   in chapter three titled Shifts and the Demand Curve.   So, let's start with the demand curve.   We've got our axis here.   We've got quantity demanded on the horizontal axis and price   of the good on the vertical axis and we're going   to look a given demand curve, D1.   And we're going to pick a point on this demand curve point A   and we're going to say that that point goes along with a price   of 20 dollars and it goes along   with a quantity demanded let's say a 500 dollars.   And then, we're going to take a point, point B, I'm going to say   that goes along with the price of 10 dollars   and a quantity demanded we're going to say of 700.   All right.   Now, we want to increase demand, what does it mean   if we increase the demand for a good?   Well, that means that individuals are willing and able   to buy more units of this good at each [inaudible] price.   So, instead of let's say buying 500 or quantity demanded 500   at 20 dollars, at 20 dollars, let's say they want to buy 600.   I want to put a point here C and it goes along   with a quantity demanded of 600.   And let's suppose that at 10 dollars,   instead of buying a quantity demanded   or having a quantity demanded of 700,   they want a quantity demanded or they want to buy 800, right?   So now, if we connect point C and D,   we get a new demand curve, all right?   So an increase in demand,   an increase in demand is diagrammatically illustrated   by rightward shift in the demand curve,   the demand curve shifts right.   Again, an increase in demand is represented diagrammatically   as rightward shift in the demand curve.   Well, what about a decrease in demand?   Let's start with a demand curve once again.   So, here is quantity demanded and price of a good and again,   we're going to draw a demand curve D1 and we're going   to pick a point, point A and we're going to say that goes   with 20 dollars and with a quantity demanded let's say   of 500.   Now, we're going to pick another price, 10 dollars and again,   that's going to go   with a certain quantity demanded let's say of 700.   Now, we have a decrease in demand   or what does a decrease in demand mean?   It means that individuals are willing and able to buy less   of the good at each and every price.   So at 20 dollars, instead of wanting to buy 500 units,   let's say they want to buy 400 units.   So, I'm going to put a point here,   I'm going to call it point C, label this point down here,   point B. I'm going to call it point C and we're going to have   that going along with 400.   And then at 10 dollars, instead of individuals wanting   to buy 700, we're going to have them want to buy 600.   So we're going to put a point right here, point D   and we're going to have   that point D correspond the 600, right?   Now, if we connect this point C and D,   we get a new demand curve D2 and this shows a decrease in demand.   So, a decrease in demand is represented   by leftward shift in that demand curve.   Let's recap.   Demand goes up, that means the demand curve shifts   to the right.   Demand goes down for a good   that means the demand curve shifts to the left.