第05章 消费者剩余和生产者剩余.ppt

第五章 消费者剩余和生产者剩余 第五章 消费者剩余和生产者剩余 完全竞争经济是有效率的资源配置方式 不必要的干预改变资源配置方式，引起效率损失 用消费者剩余和生产者剩余的变化来度量效率损失 5.1 边际量和总量  法则一：总量的变化等于其相应边际曲线下新旧量之间区域的面积  边际成本与总成本，边际收益与总收益  例： C（ q）＝ q2， MC＝ 2q 当 q从 q0增加到 q1时，总成本增加 从边际成本来看，为图 5.1阴影面积 110022102TC M C d q q d q q q    2210T C q q＝5.1 边际量和总量  推论：如果边际量等于两条边际曲线之间的垂直距离，那么对应的总量变化等于两条边际曲线之间在新旧变化量之间的区域的面积  利润＝收益－成本  边际利润，边际收益与边际成本之间的面积  MR=P，水平 10()M R M C d q  5.2 剩余量  消费者剩余  The market demand curve depicts the various quantities that buyers would be willing and able to purchase at different prices.  在任意产出水平下，需求曲线的高度都代表了消费者愿意支付的最后 1单位产品（边际单位）的价格。

 换言之，需求曲线的高度代表了市场中消费者的产品边际效用  需求曲线相当于消费者的边际效用曲线 How the Price Affects Consumer Surplus Initial consumer surplus Quantity (b) Consumer Surplus at Price P Price 0 Demand A B C D E F P1 Q1 P2 Q2 Consumer surplus to new consumers Additional consumer surplus to initial consumers 5.2 剩余量 生产者剩余 在任意产出水平下，供给曲线的高度都代表了生产者愿意接受的最后 1单位产品（边际单位）的价格 换言之，供给曲线的高度代表了行业中的产品边际成本 供给曲线即行业的边际成本曲线 How the Price Affects Producer Surplus Quantity (b) Producer Surplus at Price P Price 0 P1 B C Supply A Initial producer surplus Q1 P2 Q2 Producer surplus to new producers Additional producer surplus to initial producers D E F 5.2 剩余量 边际成本  每个厂商的边际成本等于为增加 1单位产品生产而使用的资源的市场价格  每个厂商的边际成本等于其他厂商使用相同的资源所生产的产品的最大价值 剩余量是实际生产出的产品对消费者而言的价值与使用相同资源在最优配置条件下所可能生产出的产品的价值之间的差额。

5.2 剩余量  C.S= Value to buyers – Amount paid by buyers  P.S= Amount received by sellers – Cost to sellers  Total surplus = C.S + P.S = Value to buyers – Cost to sellers  Efficiency is the property of a resource allocation of maximizing the total surplus received by all members of society Consumer and Producer Surplus in the Market Equilibrium Producer surplus Consumer surplus Price 0 Quantity Equilibrium price Equilibrium quantity Supply Demand A C B D E The Efficiency of the Equilibrium Quantity Quantity Price 0 Supply Demand Cost to sellers Cost to sellers Value to buyers Value to buyers Value to buyers is greater than cost to sellers. Value to buyers is less than cost to sellers. Equilibrium quantity 5.3 外部干预的福利成本  自由放任 laissez faire  在自由市场中，每个参与者都对价格信号做出最优的反应，因此剩余量能够最大。

价格既向消费者传达了产品的价值，也传达了生产该产品的成本  消费者  企业 尽量使用较少的成本去生产产品，资源的价格说明了生产要素的稀缺性 选择价格与边际成本之差为正的产品进行生产，商品的价格反映了消费者的偏好  外部干预的介入，使价格机制的作用不再完善  当然，某些干预手段并不会削弱价格信号机制的作用，如财富再分配 5.3.1 产量限制  限制销售的产品数量：发放销售许可证  厂商的反应：提高价格至最高可能价格  消费者的反应：减少消费量  结果：由于受到产量限制，某些互利交易没有发生，导致了福利损失  福利变化：  C.S: A+B+E—— A  P.S: C+F—— C+B  T.S: 减少 E+F Quantity Limit Quantity Price 0 Supply Demand qE qMAX PE A B C E F PMAX D 5.3.2 税收  市场： qd＝ D（ Pd）， qs＝ S（ Ps）  市场出清条件： qd＝ qs，或 D（ Pd）＝ S（ Ps） Pd和 Ps关系待定： （ 1）不存在税收时： Pd＝ Ps ，或 D（ P）＝ S（ P）， （ P*， q*） （ 2）存在税收时： Pd>Ps 5.3.2 税收 从量税：对每一单位产品征收 t美元税。

 卖方缴税（ Pd为市场价格）： Pd＝ Ps +t 市场价格 Pd的 t部分交给政府， Pd－ t（即 Ps ）归企业  买方缴税（ Ps为市场价格）： Pd＝ Ps +t消费者支付的价格由市场价格 Ps加上赋税 t  出清条件： D（ Ps+t）＝ S（ Ps），或 D（ Pd）＝ S（ Pd－ t） 5.3.2 税收 从价税：按照销售价格的一定比率 t征税 Pd＝ Ps （ 1 +t） 市场出清条件： D（ Ps（ 1 +t））＝ S（ Ps） 或 D（ Pd）＝ S（ Pd/（ 1+t）） 求得 Ps或 Pd，继而得到 Pd或 Ps和 q值 5.3.2 税收  It does not matter whether a tax on a good is levied on buyers or sellers of the good . . . the price paid by buyers rises, and the price received by sellers falls.  A tax places a wedge between the price buyers pay and the price sellers receive. Because of this tax wedge, the quantity sold falls below the level that would be sold without a tax.The size of the market for that good shrinks.  deadweight loss Figure 1 The Effects of a Tax Price buyers pay is beyond that sellers receive. Size of tax Quantity 0 Price Price buyers pay Price sellers receive Demand Supply Price without tax Quantity without tax Quantity with tax Figure 3 How a Tax Effects Welfare A F B D C E Quantity 0 Price Demand Supply = PB Q2 = PS Price buyers pay Price sellers receive = P1 Q1 Price without tax Figure 4 The Deadweight Loss Cost to sellers Value to buyers Size of tax Quantity 0 Price Demand Supply Lost gains from trade Reduction in quantity due to the tax Price without tax Q1 PB Q2 PS DETERMINANTS OF THE DEADWEIGHT LOSS  What determines whether the deadweight loss from a tax is large or small?  The magnitude of the deadweight loss depends on how much the quantity supplied and quantity demanded respond to changes in the price.  That, in turn, depends on the price elasticities of supply and demand. Tax Distortions and Elasticities (a) Inelastic Supply Price 0 Quantity Demand Supply Size of tax When supply is relatively inelastic, the deadweight loss of a tax is small. Tax Distortions and Elasticities (b) Elastic Supply Price 0 Quantity Demand Supply Size of tax When supply is relatively elastic, the deadweight loss of a tax is large. Tax Distortions and Elasticities Demand Supply (c) Inelastic Demand Price 0 Quantity Size of tax When demand is re。