1 1 消费者、生产者 与市场效率 Consumers, Producers, and the Efficiency of Markets 第7章 Chapter 7 2 再看市场均衡 Revisiting the Market Equilibrium 市场均衡价格和数量使买者和卖者的总福利 最大化吗? Do the equilibrium price and quantity maximize the total welfare of buyers and sellers? ?市场均衡反映出市场配置稀缺资源的方式。 Market equilibrium reflects the way markets allocate scarce resources. ?市场的资源配置是否令人满意，取决于福利经济 学。 Whether the market allocation is desirable is determined by welfare economics. 3 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. ?买者和卖者从参与市场中收益。 Buyers and sellers receive benefits from taking part in the market. ?市场上供求均衡可以使买者和卖者的总福利最大化。 The equilibrium in a market can maximize the total welfare of buyers and sellers. 4 福利经济学 Welfare Economics 市场均衡导致收益最大化，因此导致消 费者和生产者的总体福利的最大化。 Equilibrium in the market results in maximum benefits, and therefore maximum total welfare for both the consumers and the producers of the product. 5 福利经济学 Welfare Economics ?消费者剩余衡量买方的经济福利。 Consumer surplus measures economic welfare from the buyer’s side. ?生产者剩余衡量卖方的经济福利。 Producer surplus measures economic welfare from the seller’s side. 6 消费者剩余 Consumer Surplus ?支付意愿是买者愿意且能够为某一物品 支付的最高价格。 Willingness to pay is the maximum price that a buyer 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. 2 7 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. 8 让我们来参加一场拍卖会…… ?拍卖品：外星人的经原课本1本 ?拍卖的参加者：John, Paul, George and Ringo. ?拍卖规则：买者由低到高出价，每次加 价以10美元为最小单位。出价最高者得 到这个课本，并支付其报价。 谁得到课本，成交价是多少？ 9 买者的支付意愿 Four Possible Buyers’ Willingness to Pay... 买者 Buyer 支付意愿 Willingness to Pay John $100 Paul 80 George 70 Ringo 50 10 让我们来参加一场拍卖会…… ?John将得到课本，成交价为80（或90）美元。 ?John得到的消费者剩余（也是市场的总消费者 剩余）为： 100-80=20美元 ?假设有两本课本呢？ ?John和Paul将得到课本，成交价为70美元。 ?John得到100-70=30美元的消费者剩余；Paul得到 80-70=10美元的消费者剩余。 ?市场的总消费者剩余为30+10=40美元。 11 消费者剩余 Consumer Surplus 消费者剩余与一种物品的需求曲线密切相关。 Consumer surplus is closely related to the demand curve for a product. 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。 The market demand curve depicts the various quantities that buyers would be willing and able to purchase at different prices. 12 买者的四种可能的支付意愿 Four Possible Buyers’ Willingness to Pay... 价格 Price 买者 Buyer 需求量 Quantity Demanded More than $100 None 0 $80 to $100 John 1 $70 to $80 John, Paul 2 $50 to $70 John, Paul, George 3 $50 or less John, Paul, George, Ringo 4 3 13 用需求曲线衡量消费者剩余 Measuring Consumer Surplus with the Demand Curve... 价格 Price of Album 50 70 80 0 $100 1234数量 Quantity of Albums 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 Demand 14 用需求曲线衡量消费者剩余 Measuring Consumer Surplus with the Demand Curve... 在任何一种数量下，需求曲线给出的价格（需 求曲线的高度）表示边际买者的支付意愿；边际 买者是如果价格再高一点，就首先离开的买者。 At any quantity, the price given by the demand curve shows the willingness to pay of the marginal buyer, the buyer who who would leave the market first if the price were any higher. 由于需求曲线反应了买者的支付意愿，我们可 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. 15 用需求曲线衡量消费者剩余 Measuring Consumer Surplus with the Demand Curve... Price of Album 50 70 80 0 $100 1234 Quantity of Albums 需求 Demand John的消费者剩余 John’s consumer surplus ($20) 价格Price = $80 16 用需求曲线衡量消费者剩余 Measuring Consumer Surplus with the Demand Curve... Price of Album 50 70 80 0 $100 1234 Quantity of Albums Demand John的消费者剩余 John’s consumer surplus ($30) 总消费者剩余 Total consumer surplus ($40) 价格Price = $70 Paul的消费者剩余 Paul’s consumer surplus ($10) 17 用需求曲线衡量消费者剩余 Measuring Consumer Surplus with the Demand Curve 需求曲线以下和价格以上的面积衡 量市场的消费者剩余。 The area below the demand curve and above the price measures the consumer surplus in the market. Q 2 P 2 价格如何影响消费者剩余 How the Price Affects Consumer Surplus... 数量 Quantity 价格 Price 0 需求Demand 原来的消原来的消 费者剩余费者剩余 Initial consumer surplus 原来消费者原来消费者 的额外消费的额外消费 者剩余者剩余 Additional consumer surplus to initial consumers 新消费者的消费者 剩余Consumer surplus to new consumers Q 1 P 1 DE F B C A 4 19 消费者剩余与经济福利 Consumer Surplus and Economic Well-Being 消费者剩余，即买者愿意为一种物品支付的金 额减他们实际支付的金额，衡量了消费者从一 种物品中得到的买者自己感觉到的收益。 Consumer surplus, the amount that buyers are willing to pay for a good minus the amount they actually pay for it, measures the benefit that buyers receive from a good as the buyers themselves perceive it. 20 生产者剩余 Producer Surplus ?生产者剩余是卖者出售一种物品得到的 金额减去卖者的成本。 Producer surplus is the amount a seller is paid minus the cost of production. ?它衡量了卖者参与市场得到的收益。 It measures the benefit to sellers participating in a market. 21 四个可能的卖者的成本 The Costs of Four Possible Sellers... 卖者Seller 成本Cost Mary $900 Frida 800 Georgia 600 Grandma 500 22 生产者剩余与供给曲线 Producer Surplus and the Supply Curve ?正如消费者剩余与需求曲线密切相关，生产者剩余也 与供给曲线密切相关。 Just as consumer surplus is related to the demand curve, producer surplus is closely related to the supply curve. ?在任何一种数量上，供给曲线给出的价格表示边际卖 者的成本，这个边际卖者是如果价格再略低一点就首 先离开市场的卖者。 At any quantity, the price given by the supply curve shows the cost of the marginal seller, the seller who would leave the market first if the price were any lower. 23 四个卖者的供给量 Supply Schedule for the Four Possible Sellers... 价格 Price 卖者 Sellers 供给量 Quantity Supplied $900 or more Mary, Frida, Georgia, Grandma 4 $800 to $900 Frida, Georgia, Grandma 3 $600 to $800 Georgia, Grandma 2 $500 to $600 Grandma 1 Less than $500 None 0 24 生产者剩余与供给曲线 Producer Surplus and the Supply Curve... 数量Quantity of Houses Painted 价格 Price of House Painting 500 800 $900 0 600 1234 Grandma’s cost Georgia’s cost Frida’s cost Mary’s cost 供给Supply 5 25 供给曲线以上和价格以下的面积衡 量市场的生产者剩余。 The area below the price and above the supply curve measures the producer surplus in a market. 生产者剩余与供给曲线 Producer Surplus and the Supply Curve 26 用供给曲线衡量生产者剩余 Measuring Producer Surplus with the Supply Curve... 数量Quantity of Houses Painted 价格Price of House Painting 500 800 $900 0 600 1234 供给Supply Grandma的生产剩余 Grandma’s producer surplus ($100) 价格Price = $600 27 用供给曲线衡量生产者剩余 Measuring Producer Surplus with the Supply Curve... 数量Quantity of Houses Painted 价格Price of House Painting 500 800 $900 0 600 1234 供给Supply Grandma的生产者剩余 Grandma’s producer surplus ($300) Price = $800 Georgia的生产者剩余 Georgia’s producer surplus ($200) 总生产者剩余 Total producer surplus ($500) 28 P 2 Q 2 价格如何影响生产者剩余 How Price Affects Producer Surplus... 数量Quantity 价格Price 0 供给Supply Q 1 P 1 A B C 原来的生 产者剩余 Initial Producer surplus 原来生产者 的额外生产者剩余 Additional producer surplus to initial producers D E F 新生产者的生产者剩余 Producer surplus to new producers 29 市场均衡的评价 Evaluating the Market Equilibrium... 价格 Price 均衡价格 Equilibrium price 0 Quantity均衡数量 Equilibrium quantity A 供给Supply C B 需求Demand D E 30 市场均衡时的消费者与生产者剩余 Consumer and Producer Surplus in the Market Equilibrium 价格 Price 均衡价格 Equilibrium price 0数量Quantity均衡价格 Equilibrium quantity A 供给Supply C B 需求Demand D E 生产者剩余 Producer surplus 消费者剩余 Consumer surplus 6 31 市场效率 Market Efficiency 消费者剩余和生产者剩余可以用来回答 下列问题： Consumer surplus and producer surplus may be used to address the following question: 由自由市场决定的资源配置从某种意义 上来说是令人满意的配置吗？ Is the allocation of resources determined by free markets in any way desirable? 32 经济福利与总剩余 Economic Well-Being and Total Surplus 以及and 消费者剩余 Consumer Surplus = 买者评价 Value to buyers _ 买者支付的金 额Amount paid by buyers 生产者剩余 Producer Surplus = 卖者得到的金额 Amount received by sellers _ 卖者的 成本 Cost to sellers 33 经济福利与总剩余 Economic Well-Being and Total Surplus 或or 总剩余 Total Surplus = 买者的评 价 Value to buyers _ 卖者的 成本 Cost to sellers 总剩余 Total Surplus = 消费者剩余 Consumer Surplus 生产者剩余 Producer Surplus + 34 效率 Efficiency 当资源配置使总剩余最大化时，我 们说，这种配置达到效率。 Efficiency is achieved when the allocation of resources maximizes total surplus. 如果你是一个仁慈的社会计划者， 你将进行怎样的配置以达到效率？ 35 效率 Efficiency ?条件1：在给定的数量下，一种物品的分配使 得它…… ?由最低成本的那些卖者来生产； ?由最高评价（支付意愿）的那些买者来消 费。 ?条件2：给定上述的分配方案，该物品的数量 是使得总剩余最大的数量。 36 评价/成本($) 0 数量 Quantity 卖者成本曲线 买者评价曲线 有效率的配置 Efficient Allocation 成本最低的卖者 来生产 支付意愿最高 的买者来消费 给定任一数量 Q 有效率的数量 是多少？ 7 37 评价/成本($) 0 数量 Quantity 有效率数量 Efficient quantity 卖者成本曲线 买者评价曲线 卖者的 成本 Cost to sellers 买者的 评价 Value to buyers 买者的 评价 Value to buyers 卖者的 成本 Cost to sellers 买者的评价大于卖者的成本 Value to buyers is greater than cost to sellers. 卖者的评价小于卖者的成本 Value to buyers is less than cost to sellers. 有效率的配置 Efficient Allocation 38 评价/成本($) 0 数量 Quantity 均衡数量 ＝有效率数量 供给曲线 ＝卖者成本曲线 需求曲线 ＝买者评价曲线 市场均衡是有效率的 Market Equilibrium is Efficient 均衡分配 ＝有效率分配 39 关于市场运行结果的三大结论 Three Insights Concerning Market Outcomes ?自由市场把物品的供给分配给对这些物品评价最高 的买者。 Free markets allocate the supply of goods to the buyers who value them most highly. ?自由市场把物品的需求分配给可以以最低成本生产 这些物品的卖者。 Free markets allocate the demand for goods to the sellers who can produce them at least cost. ?自由市场的总生产量使消费者和生产者剩余最大化 Free markets produce the quantity of goods that maximizes the sum of consumer and producer surplus. 40 无效率与贸易 Inefficiency and Trade ?如果一种配置是无效率的，那么，买者或卖者 内部、买者和卖者之间的贸易好处就还没有完 全实现。 If an allocation is not efficient, then some of the gains from trade among buyers and sellers are not being realized. ?市场配置是有效率的，因为它实现了所有的贸 易好处。 41 市场的有效率性 The Efficiency of the Market ?因为市场均衡时的资源配置是有效率的，社会计划者可 以让市场自己找出结果。 Because the equilibrium outcome is an efficient allocation of resources, the social planner can leave the market outcome as he/she finds it. ?这种完全放开的政策可以用法语自由放任来表述。 This policy of leaving well enough alone goes by the French expression laissez faire. ?亚当?斯密：市场是只看不见的手 ?原理之六：市场通常是组织经济活动的好方式 42 效率与平等 Efficiency and Equity 除了效率之外，社会计划者也会关心 平等－－在不同的买者和卖者之间福 利分配的公平性。 In addition to market efficiency, a social planner might also care about equity – the fairness of the distribution of well-being among the various buyers and sellers. 8 43 例子：倒卖门票 Example: Ticket Scalping ?如果一个经济能有效地配置其稀缺资源，物品必须给与对此评价 最高的那些消费者。倒卖门票是市场如何实现有效结果的一个例子 If an economy is to allocate its scarce resources efficiently, goods must get to those consumers who value them most highly. Ticket scalping is one example of how markets reach efficient outcomes. ?倒票者购买戏剧、音乐会和运动会的门票，并以高出他们原来成 本的价格卖出这些票。通过收取市场可以承受的最高价格，倒票者 有助于保证对门票支付意愿最高的人实际上得到这些票。 Scalpers buy tickets to plays, concerts, and sports events and then sell the tickets at a price above their original cost. By charging the highest price the market will bear, scalpers help ensure that consumers with the greatest willingness to pay for the tickets actually do get them. 44 警告：假设的作用 Warning: Assumptions ?为了得出市场有效率的结论，我们作出了一些 关于市场如何运行的假设。 ?当这些假设不成立的时候，关于市场均衡有效 率的结论可能就不成立了。 ?两个重要的假设 ?市场是完全竞争的，即不存在市场势力。(Market power) ?市场结果只与买者和卖者相关，即无外部性 (externalities)。 ?市场失灵(market failures)：自由的市场不能有 效率地配置资源。 45 为什么关于市场有效率的模型 如此重要，尽管假设与现实会有距离 ?当这些假设成立的时候，关于市场均衡 有效率的结论成立 ?即使在现实中这些假设不完全成立，它 仍然为我们分析问题提供了一个基准或 标尺(benchmark)或称参照系(reference) ?有了这一基准或标尺，我们对现实的进 一步分析就有力量。 ?比如对市场势力和外部性情况的分析。 46 市场势力 Market Power ?如果市场不完全竞争，市场势力便形成。 If a market system is not perfectly competitive, market power may result. ?市场势力是影响价格的能力。 Market power is the ability to influence prices. ?市场势力可以使市场无效率，因为它会使价格 和数量偏离供求均衡点。 Market power can cause markets to be inefficient because it keeps price and quantity from the equilibrium of supply and demand. 47 外部性 Externalities ?当市场的结果影响了买者和卖者以外的人时，产生外部性 Externalities are created when a market outcome affects individuals other than buyers and sellers in that market. ?外部性使市场福利还要取决于买者评价和卖者评价之外的 其他因素。 Externalities cause welfare in a market to depend on more than just the value to the buyers and cost to the sellers. ?当买者和卖者在决定消费和生产时不考虑外部性的时候， 市场均衡可能是无效率的。 When buyers and sellers do not take externalities into account when deciding how much to consume and produce, the equilibrium in the market can be inefficient. 48 总结 Summary ?消费者剩余衡量买者参与市场的收益。 Consumer surplus measures the benefit buyers get from participating in a market. ?消费者剩余可以通过找出需求曲线以下 和价格以上的面积来计算。 Consumer surplus can be computed by finding the area below the demand curve and above the price. 9 49 总结 Summary ?生产者剩余衡量卖者参与市场的收益。 Producer surplus measures the benefit sellers get from participating in a market. ?生产者剩余可以通过找出价格以下和供给 曲线以上的面积来计算。 Producer surplus can be computed by finding the area below the price and above the supply curve. 50 总结 Summary ?使消费者与生产者剩余的总和最大化的 资源配置被称为是有效率的资源配置。 An allocation of resources that maximizes the sum of consumer and producer surplus is said to be efficient. ?政策制定者通常关心经济的效率问题， 但同时也关心平等问题。 Policymakers are often concerned with the efficiency, as well as the equity, of economic outcomes. 51 总结 Summary ?供给与需求的均衡最大化消费者与生产者剩余之和。 The equilibrium of demand and supply maximizes the sum of consumer and producer surplus. ?就好象市场这只看不见的手在指引买者和卖者在有效 率地配置资源。 This is as if the invisible hand of the marketplace leads buyers and sellers to allocate resources efficiently. ?当有市场势力和外部性时，市场不能有效率地配置资 源。 Markets do not allocate resources efficiently in the presence of market power or externalities.