昆明理工大学MBA中级微观第24章讲义垄断

ChapterTwenty-FourMonopoly垄断StructureWhatcausesmonopolyProfit-maximizingchoicesofmonopolyMarkuppricingTaxingamonopolyInefficiencyofmonopolyNaturalmonopoly(自然垄断)PureMonopolyAmonopolizedmarkethasasingleseller.Themonopolist’sdemandcurveisthe(downwardsloping)marketdemandcurve.Sothemonopolistcanalterthemarketpricebyadjustingitsoutputlevel.PureMonopolyOutputLevel,y$/outputunitp(y)Higheroutputycausesalowermarketprice,p(y).Whatcausesmonopolies?Alegalfiat;e.g.USPostalServiceApatent;e.g.anewdrugSoleownershipofaresource;e.g.atollhighwayFormationofacartel;e.g.OPECLargeeconomiesofscale;e.g.localutilitycompanies.PureMonopolySupposethatthemonopolistseekstomaximizeitseconomicprofit,Whatoutputlevely*maximizesprofit?()()().ypyycyProfit-Maximization()()().ypyycyAttheprofit-maximizingoutputlevely*dydyddypyydcydy()()()0so,fory=y*,ddypyydcydy()().y$R(y)=p(y)yProfit-Maximization$R(y)=p(y)yc(y)Profit-MaximizationyProfit-Maximization$R(y)=p(y)yc(y)y(y)Profit-Maximization$R(y)=p(y)yc(y)y(y)y*Profit-Maximization$R(y)=p(y)yc(y)y(y)y*Profit-Maximization$R(y)=p(y)yc(y)y(y)y*Profit-Maximization$R(y)=p(y)yc(y)y(y)y*Attheprofit-maximizingoutputleveltheslopesoftherevenueandtotalcostcurvesareequal;MR(y*)=MC(y*).MarginalRevenueMarginalrevenueistherate-of-changeofrevenueastheoutputlevelyincreases;MRyddypyypyydpydy()()()().MarginalRevenueMarginalrevenueistherate-of-changeofrevenueastheoutputlevelyincreases;MRyddypyypyydpydy()()()().dp(y)/dyistheslopeofthemarketinversedemandfunctionsodp(y)/dy0.ThereforeMRypyydpydypy()()()()fory0.MarginalRevenueE.g.ifp(y)=a-bythenR(y)=p(y)y=ay-by2andsoMR(y)=a-2bya-by=p(y)fory0.MarginalRevenueE.g.ifp(y)=a-bythenR(y)=p(y)y=ay-by2andsoMR(y)=a-2bya-by=p(y)fory0.p(y)=a-byaya/bMR(y)=a-2bya/2bMarginalCostMarginalcostistherate-of-changeoftotalcostastheoutputlevelyincreases;MCydcydy()().E.g.ifc(y)=F+ay+by2thenMCyy().ab2MarginalCostFyyc(y)=F+ay+by2$MC(y)=a+2by$/outputunitaProfit-Maximization;AnExampleAttheprofit-maximizingoutputlevely*,MR(y*)=MC(y*).Soifp(y)=a-byandc(y)=F+ay+by2thenMRyabyyMCy(*)**(*)22abProfit-Maximization;AnExampleAttheprofit-maximizingoutputlevely*,MR(y*)=MC(y*).Soifp(y)=a-byandifc(y)=F+ay+by2thenMRyabyyMCy(*)**(*)22abandtheprofit-maximizingoutputlevelisyab*()ab2Profit-Maximization;AnExampleAttheprofit-maximizingoutputlevely*,MR(y*)=MC(y*).Soifp(y)=a-byandifc(y)=F+ay+by2thenMRyabyyMCy(*)**(*)22abandtheprofit-maximizingoutputlevelisyab*()ab2causingthemarketpricetobepyabyabab(*)*().ab2Profit-Maximization;AnExample$/outputunityMC(y)=a+2byp(y)=a-byMR(y)=a-2byaaProfit-Maximization;AnExample$/outputunityMC(y)=a+2byp(y)=a-byMR(y)=a-2byyab*()ab2aaProfit-Maximization;AnExample$/outputunityMC(y)=a+2byp(y)=a-byMR(y)=a-2byyab*()ab2pyabab(*)()ab2aaMonopolisticPricing&Own-PriceElasticityofDemandSupposethatmarketdemandbecomeslesssensitivetochangesinprice(i.e.theown-priceelasticityofdemandbecomeslessnegative).Doesthemonopolistexploitthisbycausingthemarketpricetorise?MonopolisticPricing&Own-PriceElasticityofDemandMRyddypyypyydpydypyypydpydy()()()()()()().1MonopolisticPricing&Own-PriceElasticityofDemandMRyddypyypyydpydypyypydpydy()()()()()()().1Own-priceelasticityofdemandispyydydpy()()MonopolisticPricing&Own-PriceElasticityofDemandMRyddypyypyydpydypyypydpydy()()()()()()().1Own-priceelasticityofdemandispyydydpy()()soMRypy()().11MonopolisticPricing&Own-PriceElasticityofDemandMRypy()().11Supposethemonopolist’smarginalcostofproductionisconstant,at$k/outputunit.Foraprofit-maximumMRypyk(*)(*)11whichispyk(*).11MonopolisticPricing&Own-PriceElasticityofDemandpyk(*).11E.g.if=-3thenp(y*)=3k/2,andif=-2thenp(y*)=2k.Soasrisestowards-1themonopolistaltersitsoutputleveltomakethemarketpriceofitsproducttorise.MonopolisticPricing&Own-PriceElasticityofDemandNoticethat,sinceMRypyk(*)(*),11py(*)110MonopolisticPricing&Own-PriceElasticityofDemandNoticethat,sinceMRypyk(*)(*),11py(*)110110MonopolisticPricing&Own-PriceElasticityofDemandNoticethat,sinceMRypyk(*)(*),11py(*)110110Thatis,11MonopolisticPricing&Own-PriceElasticityofDemandNoticethat,sinceMRypyk(*)(*),11py(*)110110Thatis,111.MonopolisticPricing&Own-PriceElasticityofDemandNoticethat,sinceMRypyk(*)(*),11py(*)110110Thatis,111.Soaprofit-maximizingmonopolistalwaysselectsanoutputlevelforwhichmarketdemandisown-priceelastic.MarkupPricingMarkuppricing:Outputpriceisthemarginalcostofproductionplusa“markup.”Howbigisamonopolist’smarkupandhowdoesitchangewiththeown-priceelasticityofdemand?MarkupPricingpykpykk(*)(*)11111isthemonopolist’sprice.MarkupPricingpykpykk(*)(*)11111isthemonopolist’sprice.Themarkupispykkkk(*).11MarkupPricingpykpykk(*)(*)11111isthemonopolist’sprice.Themarkupispykkkk(*).11E.g.if=-3thenthemarkupisk/2,andif=-2thent