中级微观经济学第30章Exchange课件.ppt

《中级微观经济学第30章Exchange课件.ppt》由会员分享，可在线阅读，更多相关《中级微观经济学第30章Exchange课件.ppt（95页珍藏版）》请在淘文阁 - 分享文档赚钱的网站上搜索。

1、Chapter ThirtyExchange交换交换ContentsuThe Edgeworth(艾奇沃斯艾奇沃斯)BoxuPareto improving tradeuPareto Efficient AllocationuThe Core(核心核心)uTrade in a competitive marketuWalras Law of general equilibrium(一般均一般均衡衡)uFirst Fundamental Theorem of Welfare Economics(福利经济学第一定理福利经济学第一定理)uSecond Fundamental Theorem of W

2、elfare Economics(福利经济学第二定理福利经济学第二定理)ExchangeuTwo consumers,A and B.uTheir endowments of goods 1 and 2 are uE.g.uThe total quantities availableandandunits of good 1units of good 2.andareExchangeuEdgeworth and Bowley devised a diagram,called an Edgeworth box,to show all possible allocations of the ava

3、ilable quantities of goods 1 and 2 between the two consumers.Starting an Edgeworth BoxStarting an Edgeworth BoxWidth=Starting an Edgeworth BoxWidth=Height=Starting an Edgeworth BoxWidth=Height=The dimensions ofthe box are thequantities availableof the goods.Feasible AllocationsuWhat allocations of t

4、he 8 units of good 1 and the 6 units of good 2 are feasible?uHow can all of the feasible allocations be depicted by the Edgeworth box diagram?uOne feasible allocation is the before-trade allocation;i.e.the endowment allocation.Width=Height=The endowmentallocation isandThe Endowment AllocationWidth=H

5、eight=The Endowment AllocationOAOB68The Endowment AllocationOAOB6846The Endowment AllocationOAOB684622The Endowment AllocationOAOB684622TheendowmentallocationThe Endowment AllocationMore generally,The Endowment AllocationThe Endowment AllocationOAOBTheendowmentallocationOther Feasible Allocationsu d

6、enotes an allocation to consumer A.u denotes an allocation to consumer B.uAn allocation is feasible if and only ifandFeasible ReallocationsOAOBFeasible ReallocationsOAOBFeasible ReallocationsuAll points in the box,including the boundary,represent feasible allocations of the combined endowments.uWhic

7、h allocations will be blocked by one or both consumers?uWhich allocations make both consumers better off?Adding Preferences to the BoxOAFor consumer A.Adding Preferences to the BoxMore preferredFor consumer A.OAAdding Preferences to the BoxFor consumer B.OBAdding Preferences to the BoxMore preferred

8、For consumer B.OBAdding Preferences to the BoxMore preferredFor consumer B.OBAdding Preferences to the BoxOAFor consumer A.Adding Preferences to the BoxOAOBEdgeworths BoxOAOBPareto-ImprovementuAn allocation of the endowment that improves the welfare of a consumer without reducing the welfare of anot

9、her is a Pareto-improving allocation.uWhere are the Pareto-improving allocations?Edgeworths BoxOAOBPareto-ImprovementsOAOBThe set of Pareto-improving allocationsPareto-ImprovementsuSince each consumer can refuse to trade,the only possible outcomes from exchange are Pareto-improving allocations.uBut

10、which particular Pareto-improving allocation will be the outcome of trade?Pareto-ImprovementsOAOBThe set of Pareto-improving reallocationsPareto-ImprovementsPareto-ImprovementsPareto-ImprovementsTradeimproves bothAs and Bs welfares.This is a Pareto-improvementover the endowment allocation.Pareto-Imp

11、rovementsNew mutual gains-to-trade region is the set of all further Pareto-improving reallocations.Tradeimproves bothAs and Bs welfares.This is a Pareto-improvement(帕累托改进帕累托改进)over the endowment allocation.Pareto-ImprovementsFurther trade cannot improve both A and Bs welfares.Pareto-Optimality(帕累托最优

12、)Better forconsumer BBetter forconsumer APareto-OptimalityA is strictly better off but B is strictly worse offB is strictly betteroff but A is strictlyworse offPareto-OptimalityA is strictly better off but B is strictly worse offB is strictly betteroff but A is strictlyworse offBoth Aand B are worse

13、 offBoth A andB are worseoffPareto-OptimalityThe allocation isPareto-optimal since theonly way one consumerswelfare can be increased is todecrease the welfare of the otherconsumer.Pareto-OptimalityThe allocation isPareto-optimal since theonly way one consumerswelfare can be increased is todecrease t

14、he welfare of the otherconsumer.The Marginal Rates of Substitution Are Equal.Pareto-OptimalityuWhere are all of the Pareto-optimal allocations of the endowment?Pareto-OptimalityOAOBPareto-OptimalityOAOBAll the allocations marked bya are Pareto-optimal.Pareto-OptimalityuThe contract curve(契约线契约线)is t

15、he set of all Pareto-optimal allocations.Pareto-OptimalityOAOBAll the allocations marked bya are Pareto-optimal.The contract curvePareto-OptimalityuBut to which of the many allocations on the contract curve will consumers trade?uThat depends upon how trade is conducted.uIn perfectly competitive mark

16、ets?By one-on-one bargaining?Trade in Competitive MarketsuConsider trade in perfectly competitive markets.uEach consumer is a price-taker trying to maximize her own utility given p1,p2 and her own endowment.That is,.Trade in Competitive MarketsOAFor consumer A.Trade in Competitive MarketsuSo given p

17、1 and p2,consumer As net demands for commodities 1 and 2 areandTrade in Competitive MarketsuAnd,similarly,for consumer B Trade in Competitive MarketsFor consumer B.OBTrade in Competitive MarketsuA对商品对商品1的的总需求总需求是即期价格下其所需是即期价格下其所需要的总量；对商品要的总量；对商品1的的净需求净需求是需求总量是需求总量与其拥有的商品与其拥有的商品1的初始禀赋的差。的初始禀赋的差。uSo g

18、iven p1 and p2,consumer Bs net demands for commodities 1 and 2 areandTrade in Competitive MarketsuA general equilibrium occurs when prices p1 and p2 cause both the markets for commodities 1 and 2 to clear;i.e.andTrade in Competitive MarketsOAOBTrade in Competitive MarketsOAOBCan this PO allocation b

19、eachieved?Trade in Competitive MarketsOAOBBudget constraint for consumer ATrade in Competitive MarketsOAOBBudget constraint for consumer ATrade in Competitive MarketsOAOBBudget constraint for consumer BTrade in Competitive MarketsOAOBBudget constraint for consumer BTrade in Competitive MarketsOAOBBu

20、tTrade in Competitive MarketsOAOBandTrade in Competitive MarketsuSo at the given prices p1 and p2 there is an excess supply of commodity 1 excess demand for commodity 2.uNeither market clears so the prices p1 and p2 do not cause a general equilibrium.Trade in Competitive MarketsOAOBSo this PO alloca

21、tion cannot beachieved by competitive trading.Trade in Competitive MarketsOAOBWhich PO allocations can beachieved by competitive trading?Trade in Competitive MarketsuSince there is an excess demand for commodity 2,p2 will rise.uSince there is an excess supply of commodity 1,p1 will fall.uThe slope o

22、f the budget constraints is-p1/p2 so the budget constraints will become less steep.Trade in Competitive MarketsOAOBWhich PO allocations can beachieved by competitive trading?Trade in Competitive MarketsOAOBWhich PO allocations can beachieved by competitive trading?Trade in Competitive MarketsOAOBWhi

23、ch PO allocations can beachieved by competitive trading?Trade in Competitive MarketsOAOBBudget constraint for consumer ATrade in Competitive MarketsOAOBBudget constraint for consumer ATrade in Competitive MarketsOAOBBudget constraint for consumer BTrade in Competitive MarketsOAOBBudget constraint fo

24、r consumer BTrade in Competitive MarketsOAOBSoTrade in Competitive MarketsOAOBandTrade in Competitive MarketsuAt the new prices p1 and p2 both markets clear;there is a general equilibrium.uQuestion 1:Are prices p1 and p2 determined independently at equilibrium?uQuestion 2:Does the equilibrium exist?

25、Walras Law(瓦尔拉斯法则)u一个经济体内，在任何一个特定的市场中，如一个经济体内，在任何一个特定的市场中，如果所有的其他市场都是均衡的，那么那个特定果所有的其他市场都是均衡的，那么那个特定的市场也必然是均衡的。的市场也必然是均衡的。u总超额需求（或者超额供给）的值恒等于零，总超额需求（或者超额供给）的值恒等于零，即对所有可能的价格选择来说均为零，而不只即对所有可能的价格选择来说均为零，而不只是对均衡价格来说才为零是对均衡价格来说才为零 u如果在一个市场内供求相等，则在另一市场内如果在一个市场内供求相等，则在另一市场内供求也必然相等。供求也必然相等。Walras LawuEvery c

26、onsumers preferences are well-behaved so,for any positive prices(p1,p2),each consumer spends all of his budget.uFor consumer A:For consumer B:Walras LawSumming givesWalras LawRearranged,That is,.Walras LawThis says that the summed marketvalue of excess demands is zero forany positive prices p1 and p

27、2-this is Walras Law.Implications of Walras LawSuppose the market for commodity Ais in equilibrium;that is,ThenimpliesSo one implication of Walras Law for a two-commodity exchange economy is that if one market is in equilibrium then the other market must also be in equilibrium.In general,if there ar

28、e k markets,then only k-1 prices are determined at equilibrium.I.e.,the general equilibrium determines only relative prices.Implications of Walras LawImplications of Walras LawWhat if,for some positive prices p1 andp2,there is an excess quantity suppliedof commodity 1?That is,ThenimpliesImplications

29、 of Walras LawSo a second implication of Walras Lawfor a two-commodity exchange economyis that an excess supply in one marketimplies an excess demand in the othermarket.Existence of EquilibriumuRequire that the aggregate excess demand functions be a continuous function,which in turn require thatEach

30、 individuals demand function be continuous,orEach consumer is small relative to the market.First Fundamental Theorem of Welfare EconomicsuTrading in competitive markets achieves a particular Pareto-optimal allocation of the endowments.uThis is an example of the First Fundamental Theorem of Welfare E

31、conomics.First Fundamental Theorem of Welfare EconomicsuGiven that consumers preferences are well-behaved,trading in perfectly competitive markets implements a Pareto-optimal allocation of the economys endowment.u福利经济学第一定理：在一个充分竞争的市场，如果福利经济学第一定理：在一个充分竞争的市场，如果不存在不对称信息和外部性（不存在不对称信息和外部性（不存在我偷吃了你的奶不存在我偷

32、吃了你的奶酪你不知道，和我抽烟不会让你抽二手烟这两种情况酪你不知道，和我抽烟不会让你抽二手烟这两种情况），市场竞争实现的分配是帕雷托最优的，也就是这个，市场竞争实现的分配是帕雷托最优的，也就是这个社会不可能使任何一个人变得更满意而不伤害别人的社会不可能使任何一个人变得更满意而不伤害别人的利益。利益。（注：第一定理的一个重大漏洞是，帕雷托最优的分（注：第一定理的一个重大漏洞是，帕雷托最优的分配方式，可以是极度不均的。我拿配方式，可以是极度不均的。我拿10000万，你挣万，你挣1000块可以是帕雷托最优的块可以是帕雷托最优的）Market Socialism:The DebateuLange vs

33、.HayekuSocialism with economic planningState-ownershipGovernment chooses prices to clear marketsuAdvantage of competitive marketsInformationSecond Fundamental Theorem of Welfare Economicsu福利经济学第二定理：在所有消费者的偏好为凸性福利经济学第二定理：在所有消费者的偏好为凸性以及其他一些条件下，任何一个帕累托最优配置都以及其他一些条件下，任何一个帕累托最优配置都可以通过适当的初始配置调节之后经由完全竞争市可以

34、通过适当的初始配置调节之后经由完全竞争市场来实现（通过合理的总量税调解，任何帕雷托最场来实现（通过合理的总量税调解，任何帕雷托最优的分配都可以通过上述的竞争性市场来实现）。优的分配都可以通过上述的竞争性市场来实现）。（注：（注：第二定理说的是，如果你希望整个社会达到第二定理说的是，如果你希望整个社会达到某种理想的分配状况，你不需要让政府事无巨细的某种理想的分配状况，你不需要让政府事无巨细的进行分配，每人一套房子，每个月进行分配，每人一套房子，每个月3030斤肉之类的，斤肉之类的，那样是很麻烦的，而且很可能是没有效率的。如果那样是很麻烦的，而且很可能是没有效率的。如果需要更平均的最终分配，政府所

35、要做的，就是给穷需要更平均的最终分配，政府所要做的，就是给穷人发钱，找富人收税，然后让市场去分配那成千上人发钱，找富人收税，然后让市场去分配那成千上万的商品和服务。同时，这个税必须是总量税，换万的商品和服务。同时，这个税必须是总量税，换言之，也就是人头税。言之，也就是人头税。Second Fundamental Theorem of Welfare EconomicsuThe First Theorem is followed by a second that states that any Pareto-optimal allocation(i.e.any point on the cont

36、ract curve)can be achieved by trading in competitive markets provided that endowments are first appropriately rearranged amongst the consumers.uGiven that consumers preferences are well-behaved,for any Pareto-optimal allocation there are prices and an allocation of the total endowment that makes the Pareto-optimal allocation implementable by trading in competitive markets.Second Fundamental Theorem of Welfare Economics