完全竞争市场上的厂商均衡

教学目标Objectives：了解完全竞争的市场条件掌握完全竞争市场的需求曲线和收益曲线掌握完全竞争市场的短期均衡条件掌握完全竞争市场的长期均衡条件知识点Knowledge：完全竞争的市场条件、完全竞争市场的需求曲线和收益曲线完全竞争市场的短期均衡和长期均衡条件技能点Skills：绘制完全竞争市场均衡图pricetakeradvertisingmarketopportunitiesidealtypeadvantagesshortcomingsgovernmentNormalprofitSupernormalprofitleast-costeconomicprofitabnormalprofithomogeneousproducteconomiesofscaleindustry专业词汇Professionalterms一、完全竞争的含义与条件AssumptionslFirmsarepricetaker.lThereiscompletefreedomofentryintotheindustryfornewfirms.lAllfirmsproduceanidenticalproduct.Theproductishomogeneous,sothereisnobrandingandadvertising.lProducersandconsumershaveperfectknowledgeofthemarket.Thatis,producersarefullyawareofprices,costsandmarketopportunities.Consumersarefullyawareoftheprice,quantityandavailabilityoftheproduct.Nevertheless,despitethelackofreal-worldcases,themodelofperfectcompetitionplaysaveryimportantroleineconomicanalysisandpolicy.Itsmajorrelevanceisasan‘idealtype’.Manyonthepoliticalrightarguethatperfectcompetitionbringsanumberofimportantadvantages.Themodelcanthusbeusedasastandardagainstwhichtojudgetheshortcomingsofrealworldindustries.Itcanhelpgovernmenttoformulatepoliciestowardsindustry.一、完全竞争的含义与条件实现完全竞争的条件包括：第一，市场上有许多生产者与消费者，每一个生产者的销售量与消费者的购买量只占市场极小的份额。第二，市场上的产品是同质的，即不存在产品差别。第三，资源完全自由流动。第四，市场信息是畅通的。一、完全竞争的含义与条件TheshortrunandthelongrunlTheshortrununderperfectcompetitionTheperiodduringwhichthereistoolittletimefornewfirmstoentertheindustry.lThelongrununderperfectcompetitionTheperiodoftimethatislongenoughfornewfirmstoentertheindustry.NormalprofitTheopportunitycostofbeinginbusiness:theprofitthatcouldhavebeenearnedinthenextbestalternativebusiness.Itiscountedasacostofproduction.Supernormalprofit(alsoknownaspureprofit,economicprofit,abnormalprofitorsimplyprofit)Theexcessoftotalprofitabovenormalprofit.二、完全竞争市场上的需求和收益曲线0Q0Q0Q1Q2QTR完全竞争市场上的需求曲线与收益曲线PPP0P0DSEd(MR=AR=P)(a)(c)(b)TR2TR1TRQ三、完全竞争市场上的短期均衡完全竞争市场均衡图0QEQPEd（MR=AR=P）PESMC三、完全竞争市场上的短期均衡PESMCSACPEd（MR=AR=P）0QEQ完全竞争市场厂商盈亏平衡图厂商获得正常利润(normalprofit)三、完全竞争市场上的短期均衡厂商获得超额利润(supernormalprofit)Fd（MR=AR=P）ESMCSACPPEPF0QEQ完全竞争厂商取得超额利润分析图三、完全竞争市场上的短期均衡厂商遭受亏损SMCSACd（MR=AR=P）FEPPFPE0QEQ完全竞争亏损厂商均衡分析图三、完全竞争市场上的短期均衡ACBSMCSACAVCPPAPBPCd(AR=MR=PB)亏损企业经营规模调整分析图四、完全竞争市场上的长期均衡Revenueandcost0QuantityP=AR=MRACMCPQNORMALPROFIT五、对完全竞争市场的评论Inmanyindustries,firmsmayhavetobequitelargeiftheyaretoexperiencethefullpotentialeconomiesofscale.Butperfectcompetitionrequirestheretobemanyfirms.Firmsmustthereforebesmallinmostforeconomiesofscale.Onceafirmexpandssufficientlytoachieveeconomiesofscale,itwillusuallygainmarketpower.Itwillbeabletoundercutthepricesofsmallerfirms,whichwillthusbedrivenoutofbusiness.Perfectcompetitionisdestroyed.Perfectcompetitioncouldonlyexistinanyindustry,therefore,iftherewereno(orvirtuallyno)economiesofscale.PerfectcompetitionandthepublicinterestThereareanumberoffeaturesofperfectcompetitionwhich,itcouldbeargued,benefitsociety:lPriceequalsmarginalcost,whichhasimportantimplicationsfortheallocationofresourcesbetweenalternativeproducts.lIfafirmbecomeslessefficientthanotherfirms,itwillmakelessthannormalprofitsandbedrivenoutofbusiness.Ifitismoreefficient,itwillearnsupernormalprofits.Thusthecompetitionbetweenfirmswillactasaspurtoefficiency.lSimilarly,thedesireforsupernormalprofit,andthedesiretoavoidloss,willencouragethedevelopmentofnewtechnology.PerfectcompetitionandthepublicinterestlThereisnopointinadvertisingunderperfectcompetition,sinceallfirmsproduceahomogeneousproduct.ThisandtheprevioustwofactorswillleadtolowACcurves,andhencetoaneconomicaluseofthenation’sscarceresources.lForanygiventechnology,thefirm,inthelongrun,willproduceattheleast-costoutput.lTheconsumergainsfromlowprices,sincenotonlyarecostskeptlow,butalsotherearenolong-runsupernormalprofitstothesecosts.lIfconsumertasteschange,theresultingpricechange,theresultingpricechangewillleadfirmstorespond(purelyoutofself-interest).Anincreasedconsumerdemandwillcallforthextrasupplywithonlyashort-runincreaseinprofit.五、对完全竞争市场的评论第一，社会供给与需求相等，使资源得到最优配置，生产者的生产不会有不足或过剩，消费者的需求也得到了充分满足。第二，在长期均衡时所达到的平均成本处于最低点，表明可以通过完全竞争与资源的自由流动，使生产要素的效率得到最有效的发挥。第三，平均成本最低决定了产品的价格也是最低的，这对消费者是有利的。益处：五、对完全竞争市场的评论第一，各厂商的平均成本最低并不一定是社会成本最低。第二，产品无差别，这样，消费者的多种需求无法得到满足。第三，完全竞争市场上生产者的规模都很小，这样，他们没有能力去实现重大的科学技术突破，从而不利于科学技术发展和科技创新。第四，在实际经济生活中，完全竞争的情况是很少的，而且，一般来说，竞争也必然引起垄断。弊端：