微观经济学原理曼昆.ppt

The Market Forces of Supply and Demand
Economics
P R I N C I P L E S O F
N. Gregory Mankiw
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In this chapterQd
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Ken’s Qd
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Market Qd
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Price
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P
Q
The Market Demand Curve for Lattes
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Qd (Market)
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Demand Curve Shifters
The demand curve shows how price affects quantity demanded, other things being equal.
These “other things” are non-price determinants of demand (., things that determine buyers’ demand for a good, other than the good’s price).
Changes in them shift the D curve…
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Demand Curve Shifters: # of Buyers
Increase in # of buyers increases quantity demanded at each price, shifts D curve to the right.
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P
Q
Suppose the number of buyers increases.
Then, at each P, Qd will increase (by 5 in this example).
Demand Curve Shifters: # of Buyers
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Demand for a normal good is positively related to income.
Increase in income causes increase in quantity demanded at each price, shifts D curve to the right.
(Demand for an inferior good is negatively related to income. An increase in income shifts D curves for inferior goods to the left.)
Demand Curve Shifters: Income
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Two goods are substitutes if  an increase in the price of one  causes an increase in demand for the other.
Example: pizza and hamburgers. An increase in the price of pizza increases demand for hamburgers, shifting hamburger demand curve to the right.
Other examples: Coke and Pepsi, laptops and desktop computers, CDs and music downloads
Demand Curve Shifters: Prices of Related Goods
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Two goods are complements if  an increase in the price of one  causes a fall in demand for the other.
Example: computers and software. If price of