LECTURE5竞争性市场与一般均衡(平狄克,微观经济学-厦

,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,LECTURE 5,竞争性市场与一般均衡,1,2,完全竞争市场的条件：,价格接受者：,单个厂商产出占市场总供给的很小份额，因此无法影响市场价格；,单个消费者购买的产品占市场需求的很小份额，因此无法影响市场价格。,产品同质性：,所有厂商的产品是完全可替代的。,自由进出入：,买方可无成本地从一个厂商转向另一个厂商；,厂商可无成本进入退出某个产业。,3,消费者剩余和厂商剩余,：,在一个竞争性市场中的各自份额,，,PP5；,政府政策的财富效应：,因政府干预市场而导致的收益或损失，通过消费者剩余和厂商剩余的增减得到衡量。,政府制定价格高限，产生无谓损失,。,PP6,当消费者的需求具有足够低的弹性时，政府限价在降低厂商剩余的同时，还可能给消费者带来消费者剩余的绝对下降,。,PP7,政府制定价格低限，同样产生无谓损失。,PP8,4,Producer,Surplus,Between 0 and,Q,0,producers receive,a net gain from,selling each product-,producer surplus.,Consumer,Surplus,Quantity,0,Price,S,D,5,Q,0,Consumer C,10,7,Consumer B,Consumer A,Between 0 and,Q,0,consumers A and B,receive a net gain from,buying the product-,consumer surplus,5,The loss to producers is,the sum of rectangle,A,and triangle,C.,Triangle,B,and,C,together measure,the deadweight loss.,B,A,C,The gain to consumers is,the difference between,the rectangle,A,and the,triangle,B,.,Deadweight Loss,Quantity,Price,S,D,P,0,Q,0,P,max,Q,1,Q,2,Suppose the government,imposes a price ceiling,P,max,which is below the,market-clearing price,P,0,.,6,B,A,P,max,C,Q,1,If demand is sufficiently,inelastic, triangle,B,can,be larger than rectangle,A,and the consumer,suffers a net loss from,price controls.,Example,Oil price controls,and gasoline shortages,in 1979,S,D,Quantity,Price,P,0,Q,2,7,P,2,Q,3,A,B,C,Q,2,What would the deadweight,loss be if,Q,S,= Q,2,?,When price is,regulated to be no,lower than,P,2,only,Q,3,will be demanded. The,deadweight loss is given,by triangles,B,and,C,Quantity,Price,S,D,P,0,Q,0,8,市场失灵：,外部性：,市场价格无法反映的成本收益内容；,信息缺失：,不完美信息导致消费者无法做出效用最大化决策。,在这种情况下政府干预市场将有可能增进效率；相反，在市场并未失灵的情况下政府干预将导致市场效率降低和无谓损失。,9,B,A,The change in producer,surplus will be,A - C - D.,Producers,may be worse off.,C,D,Quantity,Price,S,D,P,0,Q,0,P,min,Q,3,Q,2,If producers produce,Q,2, the amount,Q,2,- Q,3,will go unsold.,10,B,The deadweight loss,is given by,triangles,B,and,C.,C,A,w,min,L,1,L,2,Unemployment,Firms are not allowed to,pay less than,w,min,.,This,results in unemployment.,S,D,w,0,L,0,L,w,11,价格支持：,政府制定高于均衡价格的支持价格，再由政府购买过剩的供给；,这一政策常与减产或限产的激励政策相结合。,政府成本：,Ps(Q2-Q1),无谓损失：消费者剩余,+,厂商剩余,-,政府成本,=,D-(Q2-Q1)ps,12,B,D,A,To maintain a price,P,s,the government buys,quantity,Q,g,.,The change in,consumer surplus =,-A - B,and the change in producer,surplus is,A + B + D,D + Q,g,Q,g,Quantity,Price,S,D,P,0,Q,0,P,s,Q,2,Q,1,13,D + Q,g,Q,g,B,A,Quantity,Price,S,D,P,0,Q,0,P,s,Q,2,Q,1,The cost to the,government is the,speckled rectangle,P,s,(Q,2,-Q,1,),D,Total,Welfare,Loss,Total welfare loss,D-(Q,2,-Q,1,)p,s,14,生产配额,：,通过限制供给来提高商品价格。,对农民而言，价格支持和生产配额无差别，都使他们获得,A+B+D,的额外厂商剩余；,但对政府而言，两种政策就是有差别的，哪一种政策代价更大，应比较,B+C+D,（,配额）和,Ps(Q2-Q1),（,价格支持）的大小。,15,B,A,C,D,Quantity,Price,D,P,0,Q,0,S,P,S,S,Q,1,P,s,is maintained with,and incentive,Cost to government =,B + C + D,16,B,A,Quantity,Price,D,P,0,Q,0,P,S,S,S,D,C,=,A - C + B + C + D = A + B + D.,The change in consumer and producer surplus is the same as with price supports.,=,-A - B + A + B + D - B - C - D = -B - C.,17,目的：,使进口商品国内价格高于国际价格，从而达到限制进口的目的。,进口配额或关税带来的福利损失：,国内厂商价格上涨，厂商剩余增加,A,；,消费者剩余损失由两部分构成，因国内商品价格上升而导致的损失和因进口商品价格上升而导致的损失：,A+B+C+D,18,Q,S,Q,D,P,W,Imports,A,B,C,By eliminating imports,the price is increased to,P,O,. The gain is area,A.,The,loss to consumers,A + B + C,so the deadweight loss,is,B + C.,Quantity,Price,How high would,a tariff have,to be to get the,same result?,D,P,0,Q,0,S,In a free market, the,domestic price equals the,world price,P,W,.,19,D,C,B,Q,S,Q,D,Q,S,Q,D,A,P*,P,w,Quantity,Price,D,S,The increase in price can be achieved by a quota or a tariff.,Area,A,is again the gain to domestic producers.,The loss to consumers is,A + B + C + D.,20,If a tariff is used the government gains,D,so the net domestic product loss is,B + C.,If a quota is used instead, rectangle,D,becomes part of the profits of foreign producers, and the net domestic loss is,B + C + D.,D,C,B,Q,S,Q,D,Q,S,Q,D,A,P*,P,w,Quantity,D,S,Price,21,征税：,买方价格,卖方价格,从量税征税后必须满足四个条件：,销售量和购买价格位于需求曲线上，,QD = QD(Pb),销售量和销售价格位于供给曲线上，,QS = QS(Ps),需求量,=,供给量，,QD =,QS,购买价与销售价之差为税收，,Pb - PS = tax,22,D,S,B,D,A,Buyers lose,A + B, and,sellers lose,D + C,and,the government earns,A + D,in revenue. The deadweight,loss is,B + C.,C,Quantity,Price,P,0,Q,0,Q,1,P,S,P,b,t,P,b,is the price (including,the tax) paid by buyers.,P,S,is the price sellers receive,net of the tax. The burden,of the tax is split evenly.,23,征税：,税收影响取决于供给和需求弹性；,一般来说，如,Ed/Es,较小，税负主要由买方承担，反之则由卖方承担。,转嫁因子：,ES/(ES - Ed),转嫁因子趋近于1，税负主要由消费者承担；,转嫁因子趋近于0，税负主要由厂商承担。,24,Quantity,Quantity,Price,Price,S,D,S,D,Q,0,P,0,P,0,Q,0,Q,1,P,b,P,S,t,Q,1,P,b,P,S,t,Burden on Buyer,Burden on Seller,25,补贴：,补贴可视为负税收，分析方法与上面相同。,在此种情况下，买方价格,卖方价格，,如,Ed/Es,较小，补贴的好处主要归于消费者，反之则归于厂商。,补贴的四个条件类似于征税。,26,D,S,Quantity,Price,P,0,Q,0,Q,1,P,S,P,b,s,Like a tax, the benefit,of a subsidy is split,between buyers and,sellers, depending,upon the elasticities of,supply and demand.,27,28,局部均衡：,假设一种商品市场的行为不影响其他商品市场。,一般均衡：,将市场之间的反馈效应考虑在内去同时确定所有市场的价格和数量。,反馈效应：,由相关市场的价格或数量变更而引起的一个市场的价格或数量的变更。,两个市场相互作用，最终走向一般均衡。,29,例子：,电影票和,DVD,租赁市场（互补品）。,图：,PP31-32。,结论：,未以一般均衡的观点考察市场之间的反馈效应，在这个例子里将导致低估税收效应；,这在宏观经济政策的决策中十分重要。,30,D,V,D,M,Price,Number,of Videos,Price,Number of,Movie Tickets,S,M,S,V,$6.00,Q,M,Q,V,$3.00,$6.35,Q,M,S*,M,Assume the government,imposes a $1 tax on,each movie ticket.,Q,V,D,V,$3.50,General Equilibrium Analysis:,Increase in movie ticket prices,increases demand for videos.,31,D,V,D,M,Price,Number,of Videos,Price,Number of,Movie Tickets,S,M,S,V,$6.00,Q,M,Q,V,$3.00,The Feedback,effects continue.,$3.58,Q*,V,D*,V,$6.35,Q,M,D*,M,$6.82,Q*,M,S*,M,Q,V,D,V,$3.50,D,M,Q”,M,$6.75,The increase in the price,of videos increases the,demand for movies.,32,帕累托效率：,无人可在不损害他人的前提下获益。,交换总是使双方获益的，换言之，交换总是促进帕累托改善的，直至达到帕累托效率状态，交换才停止。,33,假设：,两个消费者；两种商品；两人知道彼此的偏好（信息对称）；,0,交易费用。,埃奇沃斯盒子描述了交换发生的条件和效率的最终实现。,有效配置：,两消费者的边际替代率相等时实现，这在埃奇沃斯盒子里体现为两人的无差异曲线相切，此时实现了帕累托效率。,契约曲线：,埃奇沃斯盒子中所有两人无差异曲线相切的切点集合，它显示了所有的帕累托有效配置。,34,A,A,: U,J,1,= U,K,1,but the MRS,is not equal.,All combinations,in the shaded,area are,preferred to,A.,Gains from,trade,Karens,Clothing,Karens Food,U,K,1,U,K,2,U,K,3,Jamess,Clothing,Jamess Food,U,J,1,U,J,2,U,J,3,B,C,D,10,F,0,K,0,J,6,C,10,F,6,C,35,A,Karens,Clothing,Karens Food,U,K,1,U,K,2,U,K,3,Jamess,Clothing,Jamess Food,U,J,1,U,J,2,U,J,3,B,C,D,10,F,0,K,0,J,6,C,10,F,6,C,Is,B,efficient?,Hint: is the,MRS equal,at,B?,Is,C,efficient?,and D?,36,0,J,Jamess,Clothing,Karens,Clothing,0,K,Karens Food,Jamess Food,E,F,G,Contract,Curve,E, F, & G,are,Pareto efficient . If,a change improves,efficiency, everyone,benefits.,37,竞争性市场：,竞争性市场包含了众多的买者和卖者，因此任一方对交易条款不满，都可以很方便地另寻交易对方。,此时市场实现帕累托效率的条件是两种商品的相对价格比为,1,（对比两人模型的两人边际替代率相等）。,38,U,K,1,U,K,2,P,Price Line,P,PP,is the price line,and shows possible,combinations; slope is -1,U,J,1,U,J,2,10,F,0,K,0,J,6,C,10,F,6,C,Jamess,Clothing,Karens,Clothing,Karens Food,Jamess Food,C,A,Begin at A:,Each James buys,2C and sells 2F,Each James would,move from,Uj1 to Uj2, which,is preferred (A to C).,Begin at A:,Each Karen buys 2F and sells 2C. Each Karen would move from,UK1 to UK2, which,is preferred (A to C).,39,U,K,1,U,K,2,P,Price Line,P,U,J,1,U,J,2,10,F,0,K,0,J,6,C,10,F,6,C,Jamess,Clothing,Karens,Clothing,Karens Food,Jamess Food,At the prices chosen:,Quantity food,demanded (Karen),equals quantity,food supplied,(James)-competitive,equilibrium.,At the prices chosen:,Quantity clothing demanded,(James) equals quantity,clothing supplied (Karen),-competitive equilibrium.,C,A,40,10,F,0,K,0,J,6,C,10,F,6,C,Jamess,Clothing,Karens,Clothing,Karens Food,Jamess Food,P,Price Line,U,J,1,U,K,1,A,P,U,J,2,U,K,2,C,41,从,C,点可有如下几条结论：,两无差异曲线相切于,C,点，因此竞争性均衡配置,C,点是帕累托有效的；,此时两种商品的边际替代率等于它们的相对价格：,无差异曲线不相切则交易继续发生；,在无外部干扰的条件下竞争性均衡将自发实现；,福利经济学第一定理：在一个竞争性市场中，一切互惠交易将实现，最终的资源的均衡配置在经济上将是有效率（帕累托有效）的。,42,效用可能性边界：,显示了两消费者在契约曲线上实现了有效配置之后各自的效用水平。,效用可能性边界上的点是否还是公平的？对这一论断的判断取决于公平的定义。,43,H,*,Movement from one,combination to another,(,E,to,F,) reduces one,persons utility.,*All points on the frontier,are efficient.,Jamess Utility,O,J,O,K,E,F,G,Karens,Utility,L,*,Any point inside the,frontier (,H,) is inefficient.,*Combinations beyond the,frontier (L) are not,obtainable.,Lets compare,H,to,E,and,F.,44,考虑到公平因素，在描述个体效用时还应引入社会福利函数。,平均主义：所有社会成员得到同等数量的商品；,罗尔斯主义：使境况最糟的人效用最大化；,功利主义：使社会所有成员的总效用最大化；,市场导向：市场结果就是最公平的。,如何界定公平，取决于使用了上述的哪一种公平定义。竞争性均衡导致的帕累托有效结果可能是公平的，也可能不公平。,45,公平的配置是否也要求帕累托有效呢？,福利经济学第二定理：,如果个人的偏好是凸的，则每种有效配置（契约曲线上的每一点）对于某些商品的初始配置而言都是竞争性均衡。,任何一种被认为是公平的均衡都可以通过资源在个人之间的适当配置来实现，而这样一种配置本身并不必然产生低效率。换言之，公平与效率并非绝对矛盾。,然而，社会中所有再分配收入的计划都是有成本的；因此，在实践上，公平和效率目标之间存在非此即彼的权衡关系。,46,假设：,固定投入品：,劳动和资本；,两种产品：衣服和食物；,众多的投入要素供给者，他们通过出售其拥有的投入品获得收入；,所获得的收入用于消费衣服和食物。,显然，,在这一框架下，供给和需求（消费者的收入和开支）是紧密联系的；,一种投入品价格的变化将引发收入和需求的变化，并产生反馈效应。,47,60,F,50,F,40,L,30,L,Labor in clothing production,50,L,0,C,0,F,30,K,Capital,in clothing,production,20,L,10,L,20,K,10,K,10,L,20,L,30,L,40,L,50,L,Capital,in food,production,10,K,20,K,30,K,30,C,25,C,10,C,80,F,Labor in Food Production,B,C,D,A,Each point measures inputs,to the production,A,: 35,L,and 5,K-,Food,B,: 15,L,and 25K-Clothing,Each isoquant shows input,combinations for a given output,Food: 50, 60, & 80,Clothing: 10, 25, & 30,Efficiency,A,is inefficient,Shaded area is preferred to,A,B and C,are efficient,The,production contract curve,shows,all combinations that are efficient,48,据上图：,竞争性市场产生有效生产点。,此时所有厂商的工资率（,w,）,和资本价格（,r,）,都相等，并都实现了生产成本最小化：,MRTS,为等产量线的斜率；,竞争性均衡在生产契约曲线上；,竞争性均衡是有效率的。,49,生产可能性边界：,显示以固定数量的劳动和资本能够生产的两种商品的所有组合，即生产契约曲线上的所有产量组合。,每点的斜率表示在该生产组合时的边际转换率,MRT,。,50,Food,(Units),Clothing,(units),O,F,& O,C,are extremes.,Why is the production,possibilities frontier,downward sloping?,Why is it concave?,B, C, & D,are,other possible,combinations.,A,A,is inefficient.,ABC,triangle is also inefficient,due to labor market,distortions.,60,100,O,F,O,C,B,C,D,51,Food,(Units),Clothing,(units),60,100,O,F,O,C,A,B,C,D,B,1,C,1,F,D,2,C,1,F,MRT = MC,F,/MC,C,The marginal rate of,transformation (MRT),is the slope of the,frontier at each point.,52,产出效率：,应以最小成本生产；,并且生产的商品组合应与人们购买它们的意愿相一致。,此时实现了有效产出及帕累托有效配置，,MRS=MRT，,因此有：,53,Indifference,Curve,Food,(Units),Clothing,(units),60,100,Production,Possibilities,Frontier,MRS = MRT,C,How do you find the,MRS = MRT combination,with many consumers,who have different,indifference curves?,54,U,2,Food,(Units),Clothing,(units),60,100,A,C,1,F,1,B,C,2,F,2,A,shortage of,food and surplus,of clothing causes,the price of food,to increase and,the price of,clothing to decrease.,C,C*,F*,Adjustment continues until,P,F,= P,F,*,and,P,C,=,P,C,*;,MRT = MRS;,Q,D,= Q,S,for,food and clothing.,U,1,55,比较优势：,国家,1,生产一种商品的成本相对于生产其他商品来说比国家,2,生产该商品的成本低，国家,1,就在生产该商品方面对国家,2,具有比较优势。,绝对优势：,在所有商品生产上都占有绝对优势的国家将不会在所有商品生产上占有相对优势。,存在各自相对优势的国家就可以进行双边贸易，贸易将促使生产可能性边界外扩。,56,Holland,12,Italy,63,Cheese,(1 lb.),Wine,(1 gal.),Holland has an absolute,advantage in both products.,57,Holland,12,Italy,63,Cheese,(1 lb.),Wine,(1 gal.),Hollands comparative advantage,over Italy is in cheese: the cost of cheese,is 1/2 the cost of wine and Italys cost of,cheese is twice the cost of wine.,58,Holland,12,Italy,63,Cheese,(1 lb.),Wine,(1 gal.),Italys comparative advantage is wine,which is half the cost of cheese.,59,Holland,12,Italy,63,Cheese,(1 lb.),Wine,(1 gal.),Without Trade: Assume PW = PC in Holland & Italy.,Holland has 24 hrs. of labor-max. wine = 12 gals &,max. cheese = 24 lbs. or a combination,60,Holland,12,Italy,63,Cheese,(1 lb.),Wine,(1 gal.),With Trade: Italy produces 8 gal. and,trades 6; consumes 6 lbs. and 2 gals.,Without Trade: 3 lbs. and 2 gals.,61,Pre-trade,prices,U,1,Wine,(gallons),Cheese,(pounds),A,Without trade: production &,consumption at,A,in Holland.,MRT =,P,w,/P,C,=,2,World,prices,B,C,B,W,B,With trade (assume relative,price,P,w,= P,C,): Produce,at,B,MRT = 1,C,D,W,D,D,U,2,Consumption at,D,after trade.,Holland imports the wind,and exports cheese.,Who gains and who,loses from trade?,62,经济效率的条件：,交换的效率：,，,在竞争性市场中就是,生产中投入品使用的效率：,在竞争性市场中就是,产出市场的效率：,在竞争性市场中：,消费者在竞争性市场中实现效用最大化，必须满足,63,市场势力：,在商品市场中存在垄断，,MR ,P,；,比竞争性市场产出为少；,资源配置向其他市场；,于是导致无效率的配置。,不完全信息：,信息缺陷导致资源流动障碍。,外部性,当一种消费或生产活动对其他消费或生产活动产生不反映在市场价格中的间接效应时就存在外部性。,公共产品：,在计量消费时存在困难，于是市场对公共产品的提供将不足。,64,65,负外部性：,一个群体的行为给其他群体造成成本。,正外部性：,一个群体的行为给其他群体带来收益。,边际外部成本与边际社会成本,：,场景：钢铁厂将废水倾倒于河内，从而影响到下游渔民的生产成本。整个钢铁行业的废水倾倒与其产量相关联。,边际外部成本：下游渔民在每一水平的钢铁产量上被强加的成本。,边际社会成本：,MSC=MC+MEC,66,MC,S = MC,I,D,P,1,Aggregate,social cost of,negative,externality,P,1,q,1,Q,1,MSC,MSC,I,When there are negative,externalities, the marginal,social cost MSC is higher,than the marginal cost.,Firm output,Price,Industry output,Price,MEC,MEC,I,The differences is,the marginal external,cost MEC.,q*,P*,Q*,The industry competitive,output is,Q,1,while the efficient,level is,Q*.,The profit maximizing firm,produces at q1 while the,efficient output level is q*.,67,负外部性使一些低效率的厂商继续保留在行业内，从而导致长期尺度上的过量生产。,正外部性则可能导致生产过少。,68,MC,P,1,Repair Level,Value,D,Is research and development,discouraged by positive,externalities?,q,1,MSB,MEB,When there are positive,externalities (the benefits,of repairs to neighbors),marginal social benefits,MSB are higher than,marginal benefits,D.,q,*,P*,A self-interested home owner,invests,q,1,in repairs. The,efficient level of repairs,q*,is higher. The higher price,P,1,discourages repair.,69,假设：,市场失灵的原因是污染；,固定比例生产技术（要减少污染就必须减少生产，而产出的减少是通过征收产出税来实现的）；,通过改变技术，投入替代是可能的。,70,Level of Emissions,2,4,6,Dollars,per unit,of Emissions,0,2,4,6,8,10,12,14,16,18,20,22,24,26,MSC,MCA,E*,The efficient level of,emissions is 12 (,E*,) where,MCA = MSC.,Assume:,1) Competitive market,2) Output and emissions decisions are independent,3) Profit,maximizing,output chosen,At,E,o,the marginal,cost of abating emissions,is greater than the,marginal social cost.,E,0,At,E,1,the marginal,social cost is greater,than the marginal benefit.,E,1,Why is this more efficient,than zero emissions?,71,排放标准：,对厂商可以排放的污染物设定法定上限，并通过经济惩罚或法律惩罚来维持；,排放标准的设定将导致生产成本加大，行业总价格提高。,排放费：,对厂商每单位废气进行收费。,72,假设：,政策制定者有不对称信息；,管理成本客观上决定了对所有厂商适用同样的费率或标准。,排放费的优点：,当标准对所有厂商必须相同时，收费能以较低的成本实现同样的废气削减；,收费措施给厂商强烈的刺激去安装减少污染的新设备。,总结：,当,MSC,陡峭而,MCA,平缓时，设定排放标准占优；,在信息不完全时，设定标准使排放水平更确定，而减污成本更不确定；相反，收费使成本更确定而排放水平更不确定；,因此，哪种政策更好取决于不确定性的性质和各成本曲线的形状。,73,Firm 2s Reduced,Abatement,Costs,Firm 1s Increased,Abatement Costs,MCA,1,MCA,2,Level of,Emissions,2,4,6,Fee per,Unit of,Emissions,0,1,2,3,4,5,6,7,8,9,10,11,12,13,1,3,5,14,The cost minimizing solution,would be an abatement of 6,for firm 1 and 8 for firm 2 and,MCA,1,= MCA,2,= $3.,3.75,2.50,The impact of a standard of,abatement of 7 for both firms,is illustrated.,Not efficient because,MCA,2, MCA,1,.,If a fee of $3 was imposed,Firm 1 emissions would fall,by 6 to 8. Firm 2 emissions,would fall by 8 to 6.,MCA,1,= MCA,2,: efficient solution.,74,ABC is the increase,in social cost less the,decrease in abatement,cost.,Marginal,Social,Cost,Marginal Cost,of Abatement,Level of Emissions,Fee per,Unit of,Emissions,0,2,4,6,8,10,12,14,16,2,4,6,8,10,12,14,16,E,Based on incomplete,information standard is 9,(12.5% decrease).,ADE ,m*.,77,Amount of Glass,$,D,Price falls to,P,and,the amount of,recycled glass,increases to,M*.,S,v,S,r,S,The supply of glass is,the sum of the supply,of virgin glass (,S,r,) and,the supply of recycled,glass (,S,r,).,M,1,P,Without refunds the,price of glass is,P,and,S,r,is,M,1,.,S,r,S,P,M*,With refunds,S,r,increases,to,S,r,and,S,increases to,S.,78,产权是描述人们或厂商可以对他们的财产做什么的法律规则。,议价与经济效率,当受外部性影响的群体较少并且产权良好界定时，经济效率将在没有政府干预的情况下实现。,科斯定理：当各方能够无成本地讨价还价并对大家都有利时，无论产权如何界定，最终结果都将是有效率的。,有成本的议价,议价要求清晰界定的产权和规则。,诉诸法律：对损害起诉,对损害进行法律诉讼导致有效率的结果。,79,私人物品：,排他性：只有对商品支付价格的人才能使用该商品；,竞用性：如某人已使用了某个商品，则其他人不能再同时使用该商品。,公共物品：,不具有排他性与竞用性的物品；,公共资源：,不具有排他性但却具有竞用性的物品。,80,每个人都可免费获得的资源；该资源倾向于被过渡使用。,解决办法：界定私有产权。,81,Fish per Month,Benefits,Costs,($ per,fish),Demand,However, private costs,underestimate true cost.,The efficient level of,fish/month is,F*,where,MSC = MB (D),Marginal Social Cost,F*,Private Cost,F,C,Without control the number,of fish/month is,F,C,where,PC = MB.,82,公共产品的特点：,非竞争性：给定任何生产水平，向一个额外消费者提供该商品的边际成本为,0,；,非排他性：无法禁止人们消费该种商品。,注意：并非所有政府生产的产品都是公共产品。,公共产品的有效供给：,PP84,公共产品和市场失灵：,搭便车：公共产品使每个人都必定受益，此时每个家庭都没有激励去提供该产品；搭便车者能享受该种产品的好处而不必为它付钱。,搭便车者的存在使公共产品市场趋于失灵。,83,D,1,D,2,D,When a good is nonrival, the social marginal,benefit of consumption (,D,) , is determined by,vertically summing the individual demand,curves for the good.,Output,0,Benefits,(dollars),1,2,3,4,5,6,7,8,10,9,$4.00,$5.50,$7.00,Marginal Cost,$1.50,Efficient output occurs,where MC = MB at 2,units of output. MB is,$1.50 + $4.00 or $5.50.,84,政府生产公共产品较有利，是因为政府能够通过征收税费来支付生产成本。但当搭便车者存在时，要判断应提供的公共产品数量的多少是困难的。,在判断公共产品的供给时较常使用的是多数决定机制。,多数决定机制中，中间投票人的偏好结果总能击败其他选择而赢得选举。,多数决定机制是无效率的，因为它将每个投票者的偏好视为等同；,一个有效的结果应建立在以每个公民的偏好强度为权数来衡量其投票的基础上。,85,