曼昆《经济学原理》monopoly-(汉魅HanMei-经济金融类汇总分享)

15MonopolyWhileacompetitivefirmisapricetaker,amonopolyfirmisapricemaker.Afirmisconsideredamonopolyif...itisthesolesellerofitsproduct.itsproductdoesnothaveclosesubstitutes.WHYMONOPOLIESARISEThefundamentalcauseofmonopolyisbarrierstoentry.WHYMONOPOLIESARISEBarrierstoentryhavethreesources:Ownershipofakeyresource.Thegovernmentgivesasinglefirmtheexclusiverighttoproducesomegood.Costsofproductionmakeasingleproducermoreefficientthanalargenumberofproducers.MonopolyResourcesAlthoughexclusiveownershipofakeyresourceisapotentialsourceofmonopoly,inpracticemonopoliesrarelyariseforthisreason.Government-CreatedMonopoliesGovernmentsmayrestrictentrybygivingasinglefirmtheexclusiverighttosellaparticulargoodincertainmarkets.Government-CreatedMonopoliesPatentandcopyrightlawsaretwoimportantexamplesofhowgovernmentcreatesamonopolytoservethepublicinterest.NaturalMonopoliesAnindustryisanaturalmonopolywhenasinglefirmcansupplyagoodorservicetoanentiremarketatasmallercostthancouldtwoormorefirms.NaturalMonopoliesAnaturalmonopolyariseswhenthereareeconomiesofscaleovertherelevantrangeofoutput.Figure1EconomiesofScaleasaCauseofMonopolyCopyright©2004South-WesternQuantityofOutputAveragetotalcost0CostHOWMONOPOLIESMAKEPRODUCTIONANDPRICINGDECISIONSMonopolyversusCompetitionMonopolyIsthesoleproducerFacesadownward-slopingdemandcurveIsapricemakerReducespricetoincreasesalesCompetitiveFirmIsoneofmanyproducersFacesahorizontaldemandcurveIsapricetakerSellsasmuchoraslittleatsamepriceFigure2DemandCurvesforCompetitiveandMonopolyFirmsCopyright©2004South-WesternQuantityofOutputDemand(a)ACompetitiveFirm’sDemandCurve(b)AMonopolist’sDemandCurve0PriceQuantityofOutput0PriceDemandAMonopoly’sRevenueTotalRevenuePQ=TRAverageRevenueTR/Q=AR=PMarginalRevenueDTR/DQ=MRTable1AMonopoly’sTotal,Average,

andMarginalRevenueCopyright©2004South-WesternAMonopoly’sRevenueAMonopoly’sMarginalRevenueAmonopolist’smarginalrevenueisalwayslessthanthepriceofitsgood.Thedemandcurveisdownwardsloping.Whenamonopolydropsthepricetosellonemoreunit,therevenuereceivedfrompreviouslysoldunitsalsodecreases.AMonopoly’sRevenueAMonopoly’sMarginalRevenueWhenamonopolyincreasestheamountitsells,ithastwoeffectsontotalrevenue(P

Q).Theoutputeffect—moreoutputissold,soQishigher.Thepriceeffect—pricefalls,soPislower.Figure3DemandandMarginal-RevenueCurvesforaMonopolyCopyright©2004South-WesternQuantityofWaterPrice$11109876543210–1–2–3–4Demand(averagerevenue)Marginalrevenue12345678ProfitMaximizationAmonopolymaximizesprofitbyproducingthequantityatwhichmarginalrevenueequalsmarginalcost.Itthenusesthedemandcurvetofindthepricethatwillinduceconsumerstobuythatquantity.Figure4ProfitMaximizationforaMonopolyCopyright©2004South-WesternQuantityQQ0CostsandRevenueDemandAveragetotalcostMarginalrevenueMarginalcostMonopolypriceQMAXB1.Theintersectionofthemarginal-revenuecurveandthemarginal-costcurvedeterminestheprofit-maximizingquantity...A2....andthenthedemandcurveshowsthepriceconsistentwiththisquantity.ProfitMaximizationComparingMonopolyandCompetition

Foracompetitivefirm,priceequalsmarginalcost.P=MR=MCForamonopolyfirm,priceexceedsmarginalcost.P>MR=MCAMonopoly’sProfitProfitequalstotalrevenueminustotalcosts.Profit=TR-TCProfit=(TR/Q-TC/Q)

QProfit=(P-ATC)

Q

Figure5TheMonopolist’sProfitCopyright©2004South-WesternMonopolyprofitAveragetotalcostQuantityMonopolypriceQMAX0CostsandRevenueDemandMarginalcostMarginalrevenueAveragetotalcostBCEDAMonopolist’sProfitThemonopolistwillreceiveeconomicprofitsaslongaspriceisgreaterthanaveragetotalcost.Figure6TheMarketforDrugsCopyright©2004South-WesternQuantity0CostsandRevenueDemandMarginalrevenuePriceduringpatentlifeMonopolyquantityPriceafterpatentexpiresMarginalcostCompetitivequantityTHEWELFARECOSTOFMONOPOLYIncontrasttoacompetitivefirm,themonopolychargesapriceabovethemarginalcost.Fromthestandpointofconsumers,thishighpricemakesmonopolyundesirable.However,fromthestandpointoftheownersofthefirm,thehighpricemakesmonopolyverydesirable.Figure7TheEfficientLevelofOutputCopyright©2004South-WesternQuantity0PriceDemand(valuetobuyers)MarginalcostValuetobuyersisgreaterthancosttoseller.Valuetobuyersislessthancosttoseller.CosttomonopolistCosttomonopolistValuetobuyersValuetobuyersEfficientquantityTheDeadweightLossBecauseamonopolysetsitspriceabovemarginalcost,itplacesawedgebetweentheconsumer’swillingnesstopayandtheproducer’scost.Thiswedgecausesthequantitysoldtofallshortofthesocialoptimum.Figure8TheInefficiencyofMonopolyCopyright©2004South-WesternQuantity0PriceDeadweightlossDemandMarginalrevenueMarginalcostEfficientquantityMonopolypriceMonopolyquantityTheDeadweightLossTheInefficiencyofMonopolyThemonopolistproduceslessthanthesociallyefficientquantityofoutput.TheDeadweightLossThedeadweightlosscausedbyamonopolyissimilartothedeadweightlosscausedbyatax.Thedifferencebetweenthetwocasesisthatthegovernmentgetstherevenuefromatax,whereasaprivatefirmgetsthemonopolyprofit.PUBLICPOLICYTOWARDMONOPOLIESGovernmentrespondstotheproblemofmonopolyinoneoffourways.Makingmonopolizedindustriesmorecompetitive.Regulatingthebehaviorofmonopolies.Turningsomeprivatemonopoliesintopublicenterprises.Doingnothingatall.IncreasingCompetitionwithAntitrustLawsAntitrustlawsareacollectionofstatutesaimedatcurbingmonopolypower.Antitrustlawsgivegovernmentvariouswaystopromotecompetition.Theyallowgovernmenttopreventmergers.Theyallowgovernmenttobreakupcompanies.Theypreventcompaniesfromperformingactivitiesthatmakemarketslesscompetitive.IncreasingCompetitionwithAntitrustLawsTwoImportantAntitrustLawsShermanAntitrustAct(1890)Reducedthemarketpowerofthelargeandpowerful“trusts”ofthattimeperiod.ClaytonAct(1914)Strengthenedthegovernment’spowersandauthorizedprivatelawsuits.RegulationGovernmentmayregulatethepricesthatthemonopolycharges.Theallocationofresourceswillbeefficientifpriceissettoequalmarginalcost.Figure9Marginal-CostPricingforaNaturalMonopolyCopyright©2004South-WesternLossQuantity0PriceDemandAveragetotalcostRegulatedpriceMarginalcostAveragetotalcostRegulationInpractice,regulatorswillallowmonopoliststokeepsomeofthebenefitsfromlowercostsintheformofhigherprofit,apracticethatrequiressomedeparturefrommarginal-costpricing.PublicOwnershipRatherthanregulatinganaturalmonopolythatisrunbyaprivatefirm,thegovernmentcanrunthemonopolyitself(heUnitedStates,thegovernmentrunsthePostalService).DoingNothingGovernmentcandonothingatallifthemarketfailureisdeemedsmallcomparedtotheimperfectionsofpublicpolicies.PRICEDISCRIMINATIONPricediscriminationisthebusinesspracticeofsellingthesamegoodatdifferentpricestodifferentcustomers,eventhoughthecostsforproducingforthetwocustomersarethesame.PRICEDISCRIMINATIONPricediscriminationisnotpossiblewhenagoodissoldinacompetitivemarketsincetherearemanyfirmsallsellingatthemarketprice.Inordertopricediscriminate,thefirmmusthavesomemarketpower.PerfectPriceDiscriminationPerfectpricediscriminationreferstothesituationwhenthemonopolistknowsexactlythewillingnesstopayofeachcustomerandcanchargeeachcustomeradifferentprice.PRICEDISCRIMINATIONTwoimportanteffectsofpricediscrimination:Itcanincreasethemonopolist’sprofits.Itcanreducedeadweightloss.Figure10WelfarewithandwithoutPriceDiscriminationCopyright©2004South-WesternProfit(a)MonopolistwithSinglePricePrice0QuantityDeadweightlossDemandMarginalrevenueConsumersurplusQuantitysoldMonopolypriceMarginalcostFigure10WelfarewithandwithoutPriceDiscriminationCopyright©2004South-WesternProfit(b)MonopolistwithPerfectPriceDiscriminationPrice0QuantityDemandMarginalcostQuantitysoldPRICEDISCRIMINATIONExamplesofPriceDiscriminationMovieticketsAirlinepricesDiscountcouponsFinancialaidQuantitydiscountsCONCLUSION:THEPREVALENCEOFMONOPOLYHowprevalentaretheproblemsofmonopolies?Monopoliesarecommon.Mostfirmshavesomecontrolovertheirpricesbecauseofdifferentiatedproducts.Firmswithsubstantialmonopolypowerarerare.Fewgoodsaretrulyunique.SummaryAmonopolyisafirmthatisthesolesellerinitsmarket.Itfacesadownward-slop