曼昆微观经济学ch05
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Quantity demanded changes infinitely with any change in price The goods of perfect competition
P 3
D
Q1
Q2
Q
ELASTICITY AND ITS APPLICATION
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Perfectly Inelastic Demand
how much quantity demanded responds to the price, it is closely related to the slope of the demand curve.
The slope of a linear demand curve is constant,
P
<
0
Q
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ELASTICITY AND ITS APPLICATION
P
=
0
Q
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ELASTICITY AND ITS APPLICATION
Price Elasticity of Demand and Total Revenue
When a demand curve is elastic(a price
Quantity demanded changes by the same percentage as the price changes
P 3 2 A B
D 20
30 Q
rectangular hyperbola
ELASTICITY AND ITS APPLICATION
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Perfectly Elastic Demand
ELASTICITY AND ITS APPLICATION
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The Elasticity of Demand
Price elasticity of demand is a measure of how
much the quantity demanded of a good responds to a change in the price of that good.
Price Income Prices of related goods Tastes Expectations …
ELASTICITY AND ITS APPLICATION
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Income Elasticity of Demand
Income elasticity of demand measures how
Necessities vs. Luxuries Definition of the Market Time Horizon
ELASTICITY AND ITS APPLICATION
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The Price Elasticity of Demand and Its Determinants
CHAPTER
5
Elasticity and Its Application
Economics
PRINCIPLES OF
N. Gregory Mankiw
bannannan@
© 2009 South-Western, a part of Cengage Learning, all rights reserved
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ELASTICITY AND ITS APPLICATION
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The Midpoint Method
The midpoint formula is preferable when
calculating the price elasticity of demand because it gives the same answer regardless of the direction of the change.
ELASTICITY AND ITS APPLICATION
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The Variety of Demand Curves
Inelastic Demand
Elastic Demand Unit Elastic Demand Perfectly Inelastic Demand
Perfectly Elastic Demand
Jerry: I’d like $10 of gas What is each driver’s price elasticity of demand?
ELASTICITY AND ITS APPLICATION
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Price Elasticity of Demand and Total Revenue
as the percentage change in the quantity demanded divided by the percentage change in price.
Percentage change in Qd
—
Price elasticity of demand
=
Percentage change in P
but its elasticity is not.
ELASTICITY AND ITS APPLICATION
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ELASTICITY AND ITS APPLICATION
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The Price Elasticity of Demand and Its Determinants
Availability of Close Substitutes
Total Revenue = P x Q
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Total Revenue
P
4
P × Q=$400
D
Q
100
0
ELASTICITY AND ITS APPLICATION
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P
A F
H
E
>
B
G
C
0
Q
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ELASTICITY AND ITS APPLICATION
P
Quantity demanded does not respond to p0 4 Q
20
ELASTICITY AND ITS APPLICATION
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Slope and Elasticity
Because the price elasticity of demand measures
ELASTICITY AND ITS APPLICATION
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Income Elasticity of Demand
ELASTICITY AND ITS APPLICATION
much the quantity demanded of a good responds to a change in consumer’s income.
It is computed as the percentage change in the
quantity demanded divided by the percentage change in income.
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Elastic demand
Quantity demanded relatively flat responds strongly to price changes
P 3 2 A B D Q
Luxuries
20
50
ELASTICITY AND ITS APPLICATION
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Unit Elastic Demand
ELASTICITY AND ITS APPLICATION
4
Price elasticity of demand
=
__
Percentage change in Qd Percentage change in P
ELASTICITY AND ITS APPLICATION
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ELASTICITY AND ITS APPLICATION
Summary Price elasticity is higher when close substitutes
are available.
Price elasticity is higher for luxuries than for
necessities.
Price elasticity is higher for narrowly defined
goods than broadly defined ones.
Price elasticity is higher for longer horizon than for
shorter horizon.
ELASTICITY AND ITS APPLICATION
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Exercise
Tom: I’d like 10 gallons of gas
Why something is on sale?
Total revenue is the amount paid by buyers or
received by sellers of a good.
Computed as the price of the good times the
quantity sold.
elasticity greater than 1), a price decrease raises total revenue.
When a demand curve is inelastic(a price
elasticity less than 1), a price increase raises total revenue.