经济学原理·萨缪尔森-中山大学岭南学院ch.ppt

CH9.ImperfectCompetitionandMonopoly,A.PatternsofImperfectCompetitionImperfectCompetition:Individualsellershavesomemeasureofcontroloverthepriceoftheiroutput.,AcidTestforImperfectCompetitionIsDownwardTiltofFirmsDemandCurve,Monopoly(垄断),Asinglesellerwithcompletecontroloveranindustry.,Oligopoly（寡头）,SeveralsellersEachsellercanaffectthemarketprice.,MonopolisticCompetition（垄断竞争）,Alargenumberofsellersproducedifferentiatedproducts.Becausefirmssellslightlydifferentproducts,theycansellatslightlydifferentprices.,SourcesofMarketImperfect,Thereareeconomiesoflargescaleproductionanddecreasingcosts.Thereare“barrierstoentry”.（进入壁垒）,CostsandMarketImperfection,Thekeyiswhetherthereareeconomiesofscaleintheindustry.NaturalMonopoly（自然垄断）Thefirmhasaverageandmarginalcoststhatfallforever.,MarketStructureDependsonRelativeCostandDemandFactors,BarrierstoEntry,legalrestrictionshighcostofentryadvertisingandproductdifferentiation,B.marginalrevenueandmonopoly,Totalrevenue(TR)Averagerevenue(AR):AR=PMarginalRevenue(MR):thechangeinrevenuethatgeneratedbyanadditionalunitofsale.,MRcanbeeitherpositiveornegative.NegativeMR:Inordertoselladditionalunits,thefirmmustdecreaseitspricesomuchthatitstotalrevenuedecline.,PMRMR=P-reducedrevenueonallprevious,MarginalRevenueCurveComesfromDemandCurve,TheRelationshipofElasticityandMarginalRevenue,Ifdemandiselastic,MR0Ifdemandisunitelastic,MR=0ifdemandisinelastic,MR0,Profit-MaximizingConditions,MR=MC,PerfectCompetitionasaPolarCaseofImperfectCompetition,P=MR=MCAperfectcompetitorsddcurveanditsMRcurvecoincideashorizontallines.,Profit-MaximizingEquilibriumCanBeShownUsingEitherTotalorMarginalCurves,Margin