英文10-垄断竞争

FourTypesofIndustriesImperfectlyCompetitiveMarketsMonopolyMonopolisticCompetitionManyfirmssellingproductsthataresimilarbutnotidentical.OligopolyOnlyafewsellers,eachofferingasimilaroridenticalproducttotheothers.TheFourTypesofMarketStructureMonopolyOligopolyMonopolisticCompetitionPerfectCompetition•Tapwater•CableTV•Tennisballs•Crudeoil•Novels•Movies•Wheat•MilkNumberofFirms?TypeofProducts?ManyfirmsOnefirmFewfirmsDifferentiatedproductsIdenticalproductsMonopolisticCompetitionMonopolisticCompetitionMarketsthathavesomefeaturesofcompetitionandsomefeaturesofmonopoly.AttributesofMonopolisticCompetitionManysellersProductdifferentiationFreeentryandexit------ManySellersTherearemanyfirmscompetingforthesamegroupofcustomers.Productexamplesincludebooks,CDs,movies,computergames,restaurants,pianolessons,cookies,furniture,etc.ProductDifferentiationEachfirmproducesaproductthatisatleastslightlydifferentfromthoseofotherfirms.Ratherthanbeingapricetaker,eachfirmfacesadownward-slopingdemandcurve.FreeEntryorExitFirmscanenterorexitthemarketwithoutrestriction.Thenumberoffirmsinthemarketadjustsuntileconomicprofitsarezero.MonopolisticCompetitorsintheShortRun...(a)FirmMakesaProfitQuantity0PriceDemandMRATCProfitMCProfit-maximizingquantityPriceAveragetotalcostMonopolisticCompetitorsintheShortRun...Quantity0PriceDemandMRLosses(b)FirmMakesLossesMCATCAveragetotalcostLoss-minimizingquantityPriceMonopolisticCompetitionintheShortRunShort-runeconomicprofitsencouragenewfirmstoenterthemarket.This:Increasesthenumberofproductsoffered.Reducesdemandfacedbyfirmsalreadyinthemarket.Incumbent（传统运营商）firms’demandcurvesshifttotheleft.Demandfortheincumbentfirms’productsfall,andtheirprofitsdecline.MonopolisticCompetitionintheShortRunShort-runeconomiclossesencouragefirmstoexitthemarket.This:Decreasesthenumberofproductsoffered.Increasesdemandfacedbytheremainingfirms.Shiftstheremainingfirms’demandcurvestotheright.Increasestheremainingfirms’profits.TheLong-RunEquilibriumFirmswillenterandexituntilthefirmsaremakingexactlyzeroeconomicprofits.AMonopolisticCompetitorintheLongRun...zeroeconomicprofitsQuantityPrice0DemandMRATCMCProfit-maximizingquantityP=ATCTwoCharacteristicsofLong-RunEquilibriumAsinamonopoly,priceexceedsmarginalcost.Profitmaximizationrequiresmarginalrevenuetoequalmarginalcost.Thedownward-slopingdemandcurvemakesmarginalrevenuelessthanprice.TwoCharacteristicsofLong-RunEquilibriumAsinacompetitivemarket,priceequalsaveragetotalcost.Freeentryandexitdriveeconomicprofittozero.MonopolisticversusPerfectCompetitionTherearetwonoteworthydifferencesbetweenmonopolisticandperfectcompetition—excesscapacity（超额的产能）andmarkup（加价）.ExcessCapacityThereisexcesscapacityinmonopolisticcompetitioninthelongrun.Inmonopolisticcompetition,outputislessthantheefficientscaleofperfectcompetition.ExcessCapacity...Quantity(a)MonopolisticallyCompetitiveFirm(b)PerfectlyCompetitiveFirmQuantityPriceP=MR(demandcurve)MCATCPriceDemandMCATCExcesscapacityQuantityproducedEfficientscaleP=MCQuantityproduced=EfficientscalePExcessCapacityThereisnoexcesscapacityinperfectcompetitioninthelongrun.Freeentryresultsincompetitivefirmsproducingatthepointwhereaveragetotalcostisminimized,whichistheefficientscaleofthefirm.MarkupOverMarginalCostForacompetitivefirm,priceequalsmarginalcost.Foramonopolisticallycompetitivefirm,priceexceedsmarginalcost.MarkupOverMarginalCostBecausepriceexceedsmarginalcost,anextraunitsoldatthepostedpricemeansmoreprofitforthemonopolisticallycompetitivefirm.MarkupOverMarginalCost...Quantity(a)MonopolisticallyCompetitiveFirm(b)PerfectlyCompetitiveFirmQuantityPriceP=MCP=MR(demandcurve)MCATCQuantityproducedPriceDemandMarginalcostMCATCMRMarkupQuantityproducedMonopolisticversusPerfectCompetition...Quantity(a)MonopolisticallyCompetitiveFirm(b)PerfectlyCompetitiveFirmQuantityPriceP=MR(demandcurve)MCATCQuantityproducedEfficientscalePriceDemandMCATCP=MCExcesscapacityMarginalcostMarkupMRQuantityproduced=EfficientscaleMonopolisticCompetitionandtheWelfareofSocietyMonopolisticcompetitiondoesnothaveallthedesirablepropertiesofperfectcompetition.MonopolisticCompetitionandtheWelfareofSocietyThereisthenormaldeadweightlossofmonopolypricinginmonopolisticcompetitioncausedbythemarkupofpriceovermarginalcost.However,theadministrativeburdenofregulatingthepricingofallfirmsthatproducedifferentiatedproductswouldbeoverwhelming.MonopolisticCompetitionandtheWelfareofSocietyAnotherwayinwhichmonopolisticcompetitionmaybesociallyinefficientisthatthenumberoffirmsinthemarketmaynotbethe“ideal”one.ProductDifferentiationProductdifferentiation:theeffortbyfirmstoproducegoodsthatareslightlydifferentfromothertypesofgoods.Homogeneousproducts:goodsthathavenoproductdifferentiation;goodsthatareexactlythesame.AdvertisingWhenfirmsselldifferentiatedproductsandchargepricesabovemarginalcost,eachfirmhasanincentivetoadvertiseinordertoattractmorebuyerstoitsparticularproduct.AdvertisingFirmsthatsellhighlydifferentiatedconsumergoodstypicallyspendbetween10and20percentofrevenueonadvertising.Overall,about2percentoft