经济学原理·萨缪尔森--中山大学岭南学院ch8..ppt

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1、CH.8.AnalysisofPerfectlyCompetitiveMarketsA.SupplyBehavioroftheCompetitiveFirmtheCompetitiveFirm:maximizesprofitsprofits=totalrevenues-totalcoststheCompetitiveFirm:price-takerfacesacompletelyhorizontaldemandcurvetheextrarevenuegainedfromeachextraunitsoldisthe

2、marketpriceDemandCurveIsCompletelyElasticforaPerfectlyCompetitiveFirmSupplyDecisionofCompetitiveFirmThemaximumprofitoutputcomesatthatoutputwheremarginalcostequalsprice.MC=PFirm’sSupplycurveFirm’sSupplyCurveTravelsDowntheMCCurvetotheShutdownPoint.Firm’sSupplyC

3、urveIsItsRisingMarginalCostCureFirm’sSupplyCurveTravelsDowntheMCCurvetotheShutdownPointM：zero-profitpoint(零利润点)P=AC=MCM’:shutdownpoint（停业点）P=AVC=MCB.SupplyBehaviorinCompetitiveIndustriesmarketsupplycurve:horizontallyaddallfirms’supplycurvesAddAllFirms’SupplyC

4、urvestoDeriveMarketSupplyShort-runandlong-runequilibriumShort-runequilibrium:usethesamefixedamountofplantandequipment.Long-runequilibrium:allfactorsarevariable.EffectofIncreaseinDemandonPriceVariesinDifferentTimePeriodsThelongrunforacompetitiveindustryZero-pr

5、ofitlong-runequilibrium:P=MC=minimumlongrunAC=zero-profitpriceThelongrunequilibriuminacompetitiveindustryisonewithnoeconomicprofits.Long-RunIndustrySupplyDependsonCostConditionsC.SpecialCasesofCompetitiveMarketsdemandrule:demandforacommodity,thepricedeman

6、d,thequantitydemandedsupplyrule:supplyofacommodity,theprice,thequantityboughtandsoldConstantcostIncreasingcostsanddiminishingreturnsFixedsupplyandeconomicrentBackward-bendingsupplycurveConstant-CostCaseIncreasingcostsanddiminishingreturnsFactorswithFixe

7、dSupplyEarnRentBackward-BendingSupplyCurveShiftsinsupplyAnincreasedsupplywilldecreasePmostwhendemandisinelastic.AnincreasedsupplywillincreaseQmostwhendemandisinelastic.D.EfficiencyandEquityofCompetitiveMarketstheconceptofefficiencyEfficiencyofCompetitiveEqui

8、libriumThemarginalgaintosocietyfromthelastunitconsumed=themarginalcosttosocietyofthatlastunitproducedAtCompetitiveEquilibriumPointE,theMarginalCostsandUtilitiesofFoodAreExactlyBalancedPr