AP微观经济学5

7.PerfectCompetition1CharacteristicsNumbersofsellers:manyprice-takersAvailabilityofsubstitutes:fullysubstitutableDegreeofelasticity:perfectlyelasticSimilarityofproducts:homogeneousPricingstrategy:priceatmarketpriceBarrierstoentry/exit:noLongruneconomicprofits=0,price=minACP=MR=MCEquilibriuminaPerfectlyCompetitiveMarketThelong-runequilibriumoutputlevelforperfectlycompetitivefirmsiswhereMR=MC=ATC,whichiswhereATCisataminimum.Atthisoutput,economicprofitiszeroandonlyanormalreturnisrealized.Inequilibrium,eachfirmisproducingthequantityforwhichP=MR=MC=ATC,sothatnofirmearnseconomicprofits.QuantityPriceQuantityPriceandcostMCATCSD*P*Q*Q*P(a)Market(b)FirmShort-RunProfitMaximizationunderPerfectCompetitionShort-runequilibriumoutputMR=MCMR=P=D（pricetaker）DWL=0,市场实现最优配置MCATCPQEconomicprofitProfitmaximizingoutputRevenue(costs)QProfitmaximizingoutputTR-TCismaximumTCTRMarginalApproachTotalApproachMRShort-RunLossunderPerfectCompetitionShort-runlossPATC:economiclossAVCPATC:operatingintheshort-run,exitinthelongrunP=AVC:shutdownpointPAVC:exitinbothshort-runandlong-runQuantityPriceMCATCAVCMR=PeconomiclossesInthelongrunPQATCMCPe”Pe’PePQDSD’S’S”EE’E”E’’’1.P=MR=MC=minATC2.Economicprofit=0a.Firmb.Industry