6规模经济、不完全竞争和国际贸易.ppt

YOU ARE WELCOME!1International Economics国际经济学国际经济学主讲：余道先主讲：余道先2Chapter 6 Economies of Scale，Imperfect Competition,and International Trade规模经济、不完全竞争和国际贸易规模经济、不完全竞争和国际贸易3lIntroductionlEconomies of Scale and International Trade:An OverviewlEconomies of Scale and Market StructurelThe Theory of Imperfect CompetitionlMonopolistic Competition and TradelDumpinglThe Theory of External EconomieslExternal Economies and International TradelSummaryPreview4IntroductionlCountries engage in international trade for two basic reasons:lCountries trade because they differ either in their resources or in technology.lCountries trade in order to achieve scale economies or increasing returns in production.5Introduction（cont.）lThe Ricardian and Heckscher-Ohlin models also rely on competition to predict that all income from production is paid to owners of factors of production:no“excess”or monopoly profits exist.lBut when economies of scale exist,large firms may be more efficient than small firms,and the industry may consist of a monopoly or a few large firms.lProduction may be imperfectly competitive in the sense that excess or monopoly profits are captured by large firms.6Introduction（cont.）lTwo models of international trade in which economies of scale and imperfect competition play a crucial role:lMonopolistic competition model（垄断竞争模型）（垄断竞争模型）lDumping model（倾销模型）（倾销模型）7Economies of Scale and International Trade:An OverviewlModels of trade based on comparative advantage(e.g.Ricardian model)used the assumptions of constant returns to scale and perfect competition:lIncreasing the amount of all inputs used in the production of any commodity will increase output of that commodity in the same proportion（增加生产某（增加生产某商品所需的所有要素的投入会使该产品的产量同比例商品所需的所有要素的投入会使该产品的产量同比例增加）增加）.8Economies of Scale and International Trade:An OverviewlIn practice,many industries are characterized by economies of scale(also referred to as increasing returns).lProduction is most efficient,the larger the scale at which it takes place（规模越大，生产效率越高）（规模越大，生产效率越高）.9lUnder increasing returns to scale:lOutput grows proportionately more than the increase in all inputs（产出的增长比例比要素（产出的增长比例比要素投入增加的比例高）投入增加的比例高）.lAverage costs(costs per unit)decline with the size of the market（随着市场规模的扩张，平（随着市场规模的扩张，平均成本（单位成本）降低）均成本（单位成本）降低）.Economies of Scale and International Trade:An Overview10Economies of Scale and International Trade:An OverviewTable 6-1:Relationship of Input to Output for a Hypothetical Industry11Economies of Scale and Market StructurelEconomies of scale can be either:lExternallThe cost per unit depends on the size of the industry but not necessarily on the size of any one firm.（单位成本取决于产业规模，而并不一定由单（单位成本取决于产业规模，而并不一定由单一厂商的规模决定）一厂商的规模决定）lAn industry will typically consist of many small firms and be perfectly competitive.（一个产业是由许多小（一个产业是由许多小厂商组成的，而且是完全竞争的）厂商组成的，而且是完全竞争的）12Economies of Scale and Market StructurelInternal lThe cost per unit depends on the size of an individual firm but not necessarily on that of the industry.（单位（单位成本是由单个厂商的成本是由单个厂商的 规模决定的规模决定的，而并不一定是由其，而并不一定是由其所在产业的规模决定的）所在产业的规模决定的）lThe market structure will be imperfectly competitive with large firms having a cost advantage over small.lBoth types of scale economies are important causes of international trade.（上述两种规模经济都是引起国（上述两种规模经济都是引起国际贸易的重要原因）际贸易的重要原因）13lImperfect competitionlFirms are aware that they can influence the price of their product.lThey know that they can sell more only by reducing their price.lEach firm views itself as a price setter,choosing the price of its product,rather than a price taker.lThe simplest imperfectly competitive market structure is that of a pure monopoly,a market in which a firm faces no competition.The Theory of Imperfect Competition14lMonopoly:A Brief ReviewlMarginal revenue lThe extra revenue the firm gains from selling an additional unitlIts curve,MR,always lies below the demand curve,D.In order to sell an additional unit of output the firm must lower the price of all units sold(not just the marginal one).（为了多销售一单位产出，厂商必须降低所有为了多销售一单位产出，厂商必须降低所有(而不是最后一单位而不是最后一单位)出售产品的价格出售产品的价格）The Theory of Imperfect Competition15The Theory of Imperfect CompetitionFigure 6-1:Monopolistic Pricing and Production DecisionsDCost,C andPrice,PQuantity,QMonopoly profitsACPMQMMRMCAC16lMarginal Revenue and Price lMarginal revenue is always less than the price.lAssume that the demand curve the firm faces is a straight line:Q=A B x P (6-1)lThen the MR that the firm faces is given by:MR=P Q/B (6-2)The Theory of Imperfect Competition17The Theory of Imperfect CompetitionlAverage and Marginal CostslAverage Cost(AC)is total cost divided by output.lMarginal Cost(MC)is the amount it costs the firm to produce one extra unit.lWhen average costs decline in output,marginal cost is always less than average cost.18lSuppose the costs of a firm,C,take the form:C=F+c x Q (6-3)This is a linear cost function.The fixed cost in a linear cost function gives rise to economies of scale,because the larger the firms output,the less is fixed cost per unit.lThe firms average costs is given by:AC=C/Q=F/Q+c (6-4)The Theory of Imperfect Competition19Figure 6-2:Average Versus Marginal CostThe Theory of Imperfect CompetitionAverage costMarginal cost120345624681012141618202224Cost per unitOutput20lMonopolistic Competition（垄断竞争）（垄断竞争）lMonopolistic competition is a model of an imperfectly competitive industry which assumes that：Each firm is assumed to be able to differentiate its product from its rivals.（每个厂商均能生产与竞争对手有差（每个厂商均能生产与竞争对手有差异的产品）异的产品）Each firm is assumed to take the prices charged by its rivals as given.（每个厂商把竞争对手的价格作为既定价格）（每个厂商把竞争对手的价格作为既定价格）The Theory of Imperfect Competition21lAre there any monopolistically competitive industries in the real world?（在现实中，是否存在（在现实中，是否存在垄断竞争行业？）垄断竞争行业？）lSome industries may be reasonable approximations(e.g.,the automobile industry in Europe)lThe main appeal of the monopolistic competition model is not its realism,but its simplicity.The Theory of Imperfect Competition22lAssumptions of the ModellImagine an industry consisting of a number of firms producing differentiated products（差异产品）（差异产品）.lWe expect a firm:To sell more the larger the total demand for its industrys product and the higher the prices charged by its rivals（对（对其所在产业产品的需求越大，其竞争对手制定的价格越高，其所在产业产品的需求越大，其竞争对手制定的价格越高，该厂商销售的产品就越多）该厂商销售的产品就越多）To sell less the greater the number of firms in the industry and the higher its own price（其所在产业拥有的厂商越多，（其所在产业拥有的厂商越多，该厂商自身定价越高，销售的产品就越少）该厂商自身定价越高，销售的产品就越少）The Theory of Imperfect Competition23where:Q is the firms salesS is the total sales of the industryn is the number of firms in the industryb is a constant term representing the responsiveness of a firms sales to its priceP is the price charged by the firm itselfA particular equation for the demand facing a firm that has these properties is:Q=S x 1/n b x(P P)(6-5)The Theory of Imperfect CompetitionP is the average price charged by its competitors24lMarket EquilibriumlAll firms in this industry are symmetricThe demand function and cost function are identical for all firms.lThe method for determining the number of firms and the average price charged involves three steps:We derive a relationship between the number of firms and the average cost of a typical firm.We derive a relationship between the number of firms and the price each firm charges.We derive the equilibrium number of firms and the average price that firms charge.The Theory of Imperfect Competition251、The number of firms and average costHow do the average costs depend on the number of firms in the industry?The Theory of Imperfect CompetitionUnder symmetry,P=P,equation(6-5)tells us that Q=S/n but equation(6-4)shows us that the average cost depends inversely on a firms output.We conclude that average cost depends on the size of the market and the number of firms in the industry:AC=F/Q+c=n x F/S+c (6-6)The more firms there are in the industry the higher is the average cost.26l2、The number of firms and the pricelThe price the typical firm charges depends on the number of firms in the industry.The more firms,the more competition,and hence the lower the price.lIn the monopolistic competition model firms are assumed to take each others prices as given.The Theory of Imperfect CompetitionIf each firm treats P as given,we can rewrite the demand curve(6-5)in the form:Q=(S/n+S x b x P)S x b x P (6-7)27lProfit-maximizing firms set marginal revenue equal to their marginal cost,c.lThis generates a negative relationship between the price and the number of firms in the market which is the PP curve:P=c+1/(b x n)(6-10)The more firms there are in the industry,the lower the price each firm will charge.The Theory of Imperfect Competition28l3、The equilibrium number of firmslThe downward-sloping curve PP shows that the more firms,the lower the price each firm will charge.The more firms,the more competition each firm faces.lThe upward-sloping curve CC tells us that the more firms there are,the higher the average cost of each firm.If the number of firms increases,each firm will sell less,so firms will not be able to move as far down their average cost curve.The Theory of Imperfect Competition29PPCost C,andPrice,PNumberof firms,nCCP3AC3n3n1AC1n2 AC2EFigure 6-3:Equilibrium in a Monopolistically Competitive MarketThe Theory of Imperfect CompetitionP2,P130lLimitations of the Monopolistic Competition ModellTwo kinds of behavior arise in the general oligopoly setting that are excluded by assumption from the monopolistic competition model:lCollusive behavior（勾结行为）（勾结行为）:Can raise the profits of all firms at the expense of consumersMay be managed through explicit agreements（公开协议）（公开协议）or through tacit coordination strategies（心照不宣的合作）（心照不宣的合作）lStrategic behavior（战略行为）（战略行为）:Is adopted by firms to affect the behavior of competitors in a desirable way（引导其竞争对手向着该厂商希望的方向行动）（引导其竞争对手向着该厂商希望的方向行动）Deters potential rivals from entering an industry（阻止潜在竞争者（阻止潜在竞争者进入该行业）进入该行业）The Theory of Imperfect Competition31lThe monopolistic competition model can be used to show how trade leads to:lA lower average price due to scale economieslThe availability of a greater variety of goods due to product differentiationlImports and exports within each industry（intra-industry trade）（产业内贸易产业内贸易）Monopolistic Competition and Trade32lThe Effects of Increased Market SizelThe number of firms in a monopolistically competitive industry and the prices they charge are affected by the size of the market.（垄断竞争行业的厂商数量和价格受市场规模的影响）（垄断竞争行业的厂商数量和价格受市场规模的影响）Monopolistic Competition and Trade33lThe Effects of Increased Market SizelBecause trade increases market size,trade is predicted to decrease average cost in an industry described by monopolistic competition.lIndustry sales increase with trade leading to decreased average costs:AC=F(n/S)+clBecause trade increases the variety of goods that consumers can buy under monopolistic competition,it increases the welfare of consumers.lAnd because average costs decrease,consumers can also benefit from a decreased price.Monopolistic Competition and Trade34Figure 6-4:Effects of a Larger MarketCost C,andPrice,PNumberof firms,nCC1n1 P11PPn2P22CC2Monopolistic Competition and Trade35lGains from an Integrated Market:A Numerical ExamplelInternational trade allows creation of an integrated market that is larger than each countrys market（国际贸易可以创造出更大的市场）（国际贸易可以创造出更大的市场）.lIt thus becomes possible to offer consumers a greater variety of products and lower prices（使消费者以更低（使消费者以更低的价格获得更多的商品）的价格获得更多的商品）.Monopolistic Competition and Trade36lExample:Suppose that automobiles are produced by a monopolistically competitive industry.lAssume the following:b=1/30,000F=$750,000,000c=$5000There are two countries(Home and Foreign)that have the same costs of automobile production（相同的生产成本）（相同的生产成本）.Annual sales of automobiles are 900,000 at Home and 1.6 million at Foreign.Monopolistic Competition and Trade37Figure 6-5:Equilibrium in the Automobile MarketMonopolistic Competition and Trade38Figure 6-5:ContinuedMonopolistic Competition and Trade39Figure 6-5:ContinuedMonopolistic Competition and Trade40Table 6-2:Hypothetical Example of Gains from Market IntegrationMonopolistic Competition and Trade41lEconomies of Scale and Comparative Advantage（规模经济和比较优势）（规模经济和比较优势）lAssumptions:lThere are two countries:Home(the capital-abundant country)and Foreign.lThere are two industries:manufactures(the capital-intensive industry)and food.lNeither country is able to produce the full range of manufactured products by itself due to economies of scale（由于规模经济的存在，两个国家都不会自己生（由于规模经济的存在，两个国家都不会自己生产全部的制成品）产全部的制成品）.Monopolistic Competition and Trade42Figure 6-6:Trade in a World Without Increasing Returns（不存在收益递增时的贸易）（不存在收益递增时的贸易）Home(capital abundant)Foreign (labor abundant)ManufacturesFoodMonopolistic Competition and Trade43lIf manufactures is a monopolistically competitive sector,world trade consists of two parts（如果制造（如果制造业是垄断竞争的部门，国际贸易由以下两部分组成）业是垄断竞争的部门，国际贸易由以下两部分组成）:lIntraindustry trade（产业内贸易）（产业内贸易）The exchange of manufactures for manufactureslInterindustry trade（产业间贸易）（产业间贸易）The exchange of manufactures for foodMonopolistic Competition and Trade44Figure 6-7:Trade with Increasing Returns and Monopolistic Competition（收益递增和垄断竞争下的贸易）（收益递增和垄断竞争下的贸易）Home(capital abundant)Foreign (labor abundant)ManufacturesFoodInterindustrytradeIntraindustrytradeMonopolistic Competition and Trade45lMain differences between inter-industry and intra-industry trade:lInter-industry trade reflects comparative advantage,whereas intra-industry trade does not（产业间贸易反映了比较优势，（产业间贸易反映了比较优势，而产业内贸易没有）而产业内贸易没有）.lThe pattern of intra-industry trade itself is unpredictable,whereas that of inter-industry trade is determined by underlying differences between countries（产业内贸易模式（产业内贸易模式本身是不可预见的，而产业间贸易的模式是由国家间内在的差本身是不可预见的，而产业间贸易的模式是由国家间内在的差异性决定的）异性决定的）.Monopolistic Competition and Trade46lMain differences between inter-industry and intra-industry trade（cont.）:lThe relative importance of intra-industry and inter-industry trade depends on how similar countries are（产业内贸易和（产业内贸易和产业间贸易的相对重要性是由国家间的相似程度决定的）产业间贸易的相对重要性是由国家间的相似程度决定的）.Countries with similar relative amounts of factors of production are predicted to have intra-industry trade.Countries with different relative amounts of factors of production are predicted to have inter-industry trade.lUnlike inter-industry trade in the Heckscher-Ohlin model,income distribution effects are not predicted to occur with intra-industry trade.Monopolistic Competition and Trade47lThe Significance of Intra-industry TradelAbout one-fourth of world trade consists of intra-industry trade.lIntra-industry trade plays a particularly large role in the trade in manufactured goods among advanced industrial nations,which accounts for most of world trade.Monopolistic Competition and Trade48Table 6-3:Indexes of Intraindustry Trade for U.S.Industries,1993Monopolistic Competition and Trade49lWhy Intra-industry Trade MatterslIntra-industry trade allows countries to benefit from larger markets（产业内贸易使国家可以从更（产业内贸易使国家