经济学原理第七章

name WTP
Anthony $250 Chad Flea John
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Example: 4 buyers’ WTP for an iPod
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CONSUMERS, PRODUCERS, EFFICIENCY OF MARKETS
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WTP and the Demand Curve
good, including value of the seller’s time.
Example: Costs of 3 sellers in the lawn-cutting
business.
name Angelo Hunter
Kitty
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cost $10 20
35
A seller will only produce and sell the good if the price exceeds his or her cost. Hence, cost is a measure of willingness to sell.
Consumer Surplus (CS)
Consumer surplus is the amount a buyer is willing to pay minus the buyer actually pays:
CS = WTP – P
name WTP Suppose P = $260. Flea’s CS = $300 – 260 = $40.
Q
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CONSUMERS, PRODUCERS,Leabharlann BaiduEFFICIENCY OF MARKETS
CS with Lots of Buyers & a Smooth D Curve
At Q = 5(thousand), Price P the marginal buyer per pair $ 60 is willing to pay $50 50 for pair of shoes.
CS with Lots of Buyers & a Smooth D Curve
CS is the area b/w P and the D curve, from 0 to Q. Recall: area of a triangle equals ½ x base x height Height of this triangle is $60 – 30 = $30. So, CS = ½ x 15 x $30 = $225.
Q: If price of iPod is $200, who will buy an iPod, and what is quantity demanded?
A: Anthony & Flea will buy an iPod, Chad & John will not.
name WTP Anthony $250 Chad Flea John
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P
$ 60
The demand for shoes
50 h 40 30 20 10 0 0 5 10 15 20 25 30
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D Q
CONSUMERS, PRODUCERS, EFFICIENCY OF MARKETS
How a Higher Price Reduces CS
If P rises to $40, CS = ½ x 10 x $20 = $100. Two reasons for the fall in CS.
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Welfare economics
Recall, the allocation of resources refers to: • how much of each good is produced • which producers produce it • which consumers consume it Welfare economics:
the study of how the allocation of resources affects economic well-being
First, we look at the well-being of consumers.
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CONSUMERS, PRODUCERS, EFFICIENCY OF MARKETS
Anthony $250 Chad Flea John
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175 300 125
The others get no CS because they do not buy an iPod at this price.
Total CS = $40.
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CONSUMERS, PRODUCERS, EFFICIENCY OF MARKETS
Suppose P = $30. Then his consumer surplus = $20.
40 30 20 10 0 0
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The demand for shoes
1000s of pairs of shoes
D Q
5 10 15 20 25 30
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CONSUMERS, PRODUCERS, EFFICIENCY OF MARKETS
P
60 50 40 30
1. Fall in CS due to buyers leaving market
2. Fall in CS due to remaining buyers paying higher P
20 10 0 0 5 10 15 20 25 30
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D Q
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CONSUMERS, PRODUCERS, EFFICIENCY OF MARKETS
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Consumers, Producers, and the Efficiency of Markets
PRINCIPLES OF
MICROECONOMICS
FOURTH EDITION
N. G R E G O R Y M A N K I W
PowerPoint® Slides by Ron Cronovich
P (price of iPod)
who buys Qd 0
$301 & up nobody
251 – 300 Flea
176 – 250 Anthony, Flea Chad, Anthony, 126 – 175 Flea John, Chad, 0 – 125 Anthony, Flea
1
2 3 4
ACTIVE LEARNING
Consumer surplus 50 P
A. Find marginal buyer’s WTP at Q = 10. $ 45
1:
demand curve
40 35 B. Find CS for 30 P = $30. 25 Suppose P falls to $20. 20 How much will CS 15 increase due to… 10 C. buyers entering 5 the market 0 D. existing buyers 0 paying lower price
Total CS = $110
Q
1
2
3
4
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CONSUMERS, PRODUCERS, EFFICIENCY OF MARKETS
CS and the Demand Curve
P
$350 $300 $250 $200 $150 $100 $50 $0 0
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The lesson: Total CS equals the area under the demand curve above the price, from 0 to Q.
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Hence, Qd = 2 when P = $200.
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CONSUMERS, PRODUCERS, EFFICIENCY OF MARKETS
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WTP and the Demand Curve
Derive the demand schedule:
name WTP
CS and the Demand Curve
P
$350 $300 $250 $200 $150 $100 $50 $0 0
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Flea’s WTP
Anthony’s WTP
Instead, suppose P = $220
Flea’s CS = $300 – 220 = $80 Anthony’s CS = $250 – 220 = $30
1
Willingness to Pay (WTP)
A buyer’s willingness to pay for a good is the maximum amount the buyer will pay for that good.
WTP measures how much the buyer values the good.
At any Q, the height of the D curve is the WTP of the marginal buyer, the buyer who would leave the market if P were any higher.
Q
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CONSUMERS, PRODUCERS, EFFICIENCY OF MARKETS
5
10
15
20
Q 25
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Cost and the Supply Curve
Cost is the value of everything a seller must give
up to produce a good (i.e., opportunity cost).
Includes cost of all resources used to produce
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This D curve looks like a staircase with 4 steps – one per buyer. If there were a huge # of buyers, as in a competitive market, there would be a huge # of very tiny steps, and it would look more like a smooth curve.
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P $301 & up
Qd 0
251 – 300
176 – 250 126 – 175
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Q
0 – 125
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CONSUMERS, PRODUCERS, EFFICIENCY OF MARKETS
About the Staircase Shape…
P
$350 $300 $250 $200 $150 $100 $50 $0 0
4
Anthony $250 Chad Flea John
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175 300 125
CONSUMERS, PRODUCERS, EFFICIENCY OF MARKETS
WTP and the Demand Curve
P
$350 $300 $250 $200 $150 $100 $50 $0 0
Q
1
2
3
4
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CONSUMERS, PRODUCERS, EFFICIENCY OF MARKETS
WTP and the Demand Curve
P
$350 $300 $250 $200 $150 $100 $50 $0 0
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Flea’s WTP
Anthony’s WTP
Chad’s WTP John’s WTP
CS and the Demand Curve
P
$350 $300 $250 $200 $150 $100 $50 $0 0
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Flea’s WTP
P = $260
Flea’s CS = $300 – 260 = $40
Total CS = $40
Q
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CONSUMERS, PRODUCERS, EFFICIENCY OF MARKETS
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CONSUMERS, PRODUCERS, EFFICIENCY OF MARKETS
Cost and the Supply Curve