20
价格如何影响消费者剩余
价格 Price
How the Price Affects Consumer Surplus...
A
原来的消 费者剩余
P1
Initial consumer surplus
B
C
P2
D
原来消费者 的额外消费 者剩余
E
F
新消费者的消费者 剩余Consumer surplus to new consumers
16
用需求曲线衡量消费者剩余
Measuring Consumer Surplus with the Demand (or WTP) Curve...
由于需求曲线反映了买者的支付意愿， 我们也可以用它衡量消费者剩余。 Because the demand curve reflects buyers’ willingness to pay, we can also use it to measure consumer surplus.
7
买者的支付意愿
Four Possible Buyers’ Willingness to Pay (WTP)...
买者 Buyer John Paul George Ringo 支付意愿 Willingness to Pay $100 80 70 50
8
买者支付意愿曲线 Buyer’s WTP Curve
需求或支付意愿 Demand or WTP
0
1
2
3
4
Quantity of Albums
19
用需求曲线衡量消费者剩余 Measuring Consumer Surplus with the Demand Curve 需求（或支付意愿）曲线以下和价 格以上的面积衡量市场上的消费者 剩余。 The area below the demand (or WTP) curve and above the price measures the consumer surplus in the market.
11
买者支付意愿曲线与需求曲线 Buyer’s WTP Curve and Demand Curve
回顾：市场需求曲线画出了在不同的价 格下，买者愿意和能够购买的数量。 Recall that the market demand curve depicts the various quantities that buyers would be willing and able to purchase at different prices.
0 1 2 3 4
13
John, Paul John, Paul, George
John, Paul, George, Ringo
需求曲线
Demand Curve...
价格 Price of Album $100
80 70 50
当价格大于100时， 需求量等于零。 当价格小于100大于80时， 需求量等于1。 当价格小于80大于70时， 需求量等于2。 当价格小于70大于50时， 需求量等于3。 当价格小于50时， 需求量等于4。
9
买者支付意愿曲线
Buyer’s WTP Curve……
价格 Price of Album $100
80 70 50 John的支付意愿 John’s willingness to pay Paul的支付意愿 Paul’s willingness to pay George的支付意愿 George’s willingness to pay Ringo的支付意愿 Ringo’s willingness to pay
需求或支付意愿 Demand or WTP
0 1 2 3 4 Quantity of Albums
18
用需求曲线衡量消费者剩余
Measuring Consumer Surplus with the Demand Curve...
Price of Album
$100 80 70 50
价格Price = $70
买者支付意愿曲线（Buyer’s WTP curve） 或买者评价曲线（Buyer’s value curve）表 示市场上所有买者对每新增一单位物品的 最大可能的支付意愿。 以数量为横轴，以支付意愿（价格）为纵 轴，将市场上所有买者（在不同数量上） 的支付意愿由高至低依次标示出来，就构 成了该物品的买者支付意愿曲线。
第七章 Chapter 7 市场效率 Efficiency of Markets
再看市场均衡 Revisiting the Market Equilibrium
在市场经济中，供给和需求的力量决定物品和服 务的价格与销售量。 In market economies, the forces of supply and demand determine the prices of goods and services and the quantity sold. 市场均衡反映出社会配置稀缺资源的方式。 Market equilibrium reflects the way society allocates scarce resources. 到目前为止，我们的分析都是实证的（是什么） 而不是规范的（应该是什么）。 So far, our analysis has been positive (what is) rather than normative (what should be).
2
福利经济学 Welfare Economics
福利经济学研究资源配置如何影响经济 福利。 Welfare economics is the study of how the allocation of resources affects economic well-being.
3
ห้องสมุดไป่ตู้
福利经济学与市场均衡 Welfare Economics and Market Equilibrium
15
消费者剩余
Consumer Surplus
消费者剩余是买者的支付意愿减 买者的实际支付额。 Consumer surplus is the amount a buyer is willing to pay for a good minus the amount the buyer actually pays for it.
17
用需求曲线衡量消费者剩余
Measuring Consumer Surplus with the Demand Curve...
Price of Album
$100 80 70 50 价格Price = $80
John的消费者剩余 John’s consumer surplus ($20) Paul的消费者剩余 Paul’s consumer surplus ($0)
买者支付意愿 Buyer’s WTP
0 1 2 3 4 数量 Quantity of Albums
10
买者支付意愿曲线 Buyer’s WTP Curve
在任何一种数量下，买者支付意愿曲线 的高度表示边际买者的支付意愿。 At any quantity, the price given by the buyer’s WTP curve shows the willingness to pay of the marginal buyer. 边际买者是如果价格再高一点就首先离 开的买者。 A marginal buyer is one who would leave the market first if the price were any higher.
市场均衡导致社会总体的收益（或福 利）最大化。 Equilibrium in the market results in maximum total social benefits (or welfare).
4
福利经济学与市场均衡 Welfare Economics and Market Equilibrium
5
福利经济学：基本概念 Welfare Economics: Basic Concepts
支付意愿和消费者剩余衡量买方（消费者 ）的经济福利。 Willingness to pay and consumer surplus measures economic welfare from the buyer’s side. 成本和生产者剩余衡量卖方（生产者）的 经济福利。 Cost and Producer surplus measures economic welfare from the seller’s side.
John的消费者剩余 John’s consumer surplus ($30)
Paul的消费者剩余 Paul’s consumer surplus ($10) George的消费者剩余 总消费者剩余 George’s consumer surplus ($0) Total consumer surplus ($40)
需求 Demand
0 1 2 3 4
数量 Quantity of Albums
14
买者支付意愿曲线与需求曲线 Buyer’s WTP Curve and Demand Curve
市场需求曲线恰好反映了市场上买者的 （边际）支付意愿（两条曲线重合）。 The market demand curve exactly reflects (marginal) buyers’ willingness to pay in the market.
6
买者支付意愿 Buyer’s Willingness to Pay
支付意愿是买者（消费者）愿意且能够 为某一物品支付的最高价格。 Willingness to pay (WTP) is the maximum price that a buyer (consumer) is willing and able to pay for a good. 它衡量买者对物品或服务的评价是多少 It measures how much the buyer values the good or service.