中级微观济学课件尼科尔森ch13

柯孔林浙江工商大学金融学院1Chapter13MODELSOFMONOPOLY柯孔林浙江工商大学金融学院2BarrierstoEntryThereasonamonopolyexistsisthatotherfirmsfinditunprofitableorimpossibletoenterthemarketBarrierstoentryarethesourceofallmonopolypowertherearetwogeneraltypesofbarrierstoentrytechnicalbarrierslegalbarriers柯孔林浙江工商大学金融学院3TechnicalBarrierstoEntryTheproductionofagoodmayexhibitdecreasingmarginalandaveragecostsoverawiderangeofoutputlevelsinthissituation,relativelylarge-scalefirmsarelow-costproducersfirmsmayfinditprofitabletodriveothersoutoftheindustrybycuttingpricesthissituationisknownasnaturalmonopolyoncethemonopolyisestablished,entryofnewfirmswillbedifficult柯孔林浙江工商大学金融学院4TechnicalBarrierstoEntryAnothertechnicalbasisofmonopolyisspecialknowledgeofalow-costproductivetechniqueitmaybedifficulttokeepthisknowledgeoutofthehandsofotherfirmsOwnershipofuniqueresourcesmayalsobealastingbasisformaintainingamonopoly柯孔林浙江工商大学金融学院5LegalBarrierstoEntryManypuremonopoliesarecreatedasamatteroflawwithapatent,thebasictechnologyforaproductisassignedtoonefirmthegovernmentmayalsoawardafirmanexclusivefranchisetoserveamarket柯孔林浙江工商大学金融学院6CProfitscanbefoundintheshadedrectangleProfitMaximizationACMCDMRQuantityPriceQ*ThemonopolistwillmaximizeprofitswhereMR=MCP*ThefirmwillchargeapriceofP*柯孔林浙江工商大学金融学院7TheInverseElasticityRuleThegapbetweenafirm’spriceanditsmarginalcostisinverselyrelatedtothepriceelasticityofdemandfacingthefirm

whereeQ,Pistheelasticityofdemandfortheentiremarket柯孔林浙江工商大学金融学院8TheInverseElasticityRuleTwogeneralconclusionsaboutmonopolypricingcanbedrawn:amonopolywillchoosetooperateonlyinregionswherethemarketdemandcurveiselasticeQ,P<-1thefirm’s“markup”overmarginalcostdependsinverselyontheelasticityofmarketdemand柯孔林浙江工商大学金融学院9MonopolyProfitsMonopolyprofitswillbepositiveaslongasP>ACMonopolyprofitscancontinueintothelongrunbecauseentryisnotpossiblesomeeconomistsrefertotheprofitsthatamonopolyearnsinthelongrunasmonopolyrentsthereturntothefactorthatformsthebasisofthemonopoly柯孔林浙江工商大学金融学院10MonopolyProfitsQuantityPriceMCACMRDQuantityPriceMCACMRDPositiveprofitsZeroprofitP*P*=ACCQ*Q*柯孔林浙江工商大学金融学院11NoMonopolySupplyCurveWithafixedmarketdemandcurve,thesupply“curve”foramonopolistwillonlybeonepointtheprice-outputcombinationwhereMR=MCIfthedemandcurveshifts,themarginalrevenuecurveshiftsandanewprofit-maximizingoutputwillbechosen柯孔林浙江工商大学金融学院12MonopolyandResourceAllocationToevaluatetheallocationaleffectofamonopoly,wewilluseaperfectlycompetitive,constant-costindustryasabasisofcomparisontheindustry’slong-runsupplycurveisinfinitelyelasticwithapriceequaltobothmarginalandaveragecost柯孔林浙江工商大学金融学院13MonopolyandResourceAllocationQuantityPriceMC=ACDMRIfthismarketwascompetitive,outputwouldbeQ*andpricewouldbeP*Q*P*Underamonopoly,outputwouldbeQ**andpricewouldrisetoP**Q**P**柯孔林浙江工商大学金融学院14ConsumersurpluswouldfallProducersurpluswillriseThereisadeadweightlossfrommonopolyMonopolyandResourceAllocationQuantityPriceMC=ACDMRQ*Q**P*P**Consumersurplusfallsbymorethanproducersurplusrises.柯孔林浙江工商大学金融学院15WelfareLossesandElasticityAssumethattheconstantmarginal(andaverage)costsforamonopolistaregivenbycandthatthecompensateddemandcurvehasaconstantelasticity:Q=Pewhereeisthepriceelasticityofdemand(e<-1)柯孔林浙江工商大学金融学院16WelfareLossesandElasticityThecompetitivepriceinthismarketwillbePc=candthemonopolypriceisgivenby柯孔林浙江工商大学金融学院17WelfareLossesandElasticityTheconsumersurplusassociatedwithanyprice(P0)canbecomputedas柯孔林浙江工商大学金融学院18WelfareLossesandElasticityTherefore,underperfectcompetition

andundermonopoly柯孔林浙江工商大学金融学院19WelfareLossesandElasticityTakingtheratioofthesetwosurplusmeasuresyieldsIfe=-2,thisratiois½consumersurplusundermonopolyishalfwhatitisunderperfectcompetition柯孔林浙江工商大学金融学院20WelfareLossesandElasticityMonopolyprofitsaregivenby柯孔林浙江工商大学金融学院21WelfareLossesandElasticityTofindthetransferfromconsumersurplusintomonopolyprofitswecandividemonopolyprofitsbythecompetitiveconsumersurplusIfe=-2,thisratiois¼柯孔林浙江工商大学金融学院22MonopolyandProductQualitySupposethatconsumers’willingnesstopayforquality(X)isgivenbytheinversedemandfunctionP(Q,X)where

P/Q<0andP/X>0IfcostsaregivenbyC(Q,X),themonopolywillchooseQandXtomaximize=P(Q,X)Q-C(Q,X)柯孔林浙江工商大学金融学院23MonopolyandProductQualityFirst-orderconditionsforamaximumareMR=MCforoutputdecisionsMarginalrevenuefromincreasingqualitybyoneunitisequaltothemarginalcostofmakingsuchanincrease柯孔林浙江工商大学金融学院24MonopolyandProductQualityThelevelofproductqualitythatwillbeoptedforundercompetitiveconditionsistheonethatmaximizesnetsocialwelfareMaximizingwithrespecttoXyields柯孔林浙江工商大学金融学院25MonopolyandProductQualityThedifferencebetweenthequalitychoiceofacompetitiveindustryandthemonopolistis:themonopolistlooksatthemarginalvaluationofonemoreunitofqualityassumingthatQisatitsprofit-maximizinglevelthequalityruleadoptedtomaximizenetwelfareunderperfectcompetition.柯孔林浙江工商大学金融学院26PriceDiscriminationAmonopolyengagesinpricediscriminationifitisabletosellotherwiseidenticalunitsofoutputatdifferentpricesWhetherapricediscriminationstrategyisfeasibledependsontheinabilityofbuyerstopracticearbitrageprofit-seekingmiddlemenwilldestroyanydiscriminatorypricingschemeifpossiblepricediscriminationespossibleifresaleiscostly柯孔林浙江工商大学金融学院27PerfectPriceDiscriminationIfeachbuyercanbeseparatelyidentifiedbythemonopolist,itmaybepossibletochargeeachbuyerthemaximumpricehewouldbewillingtopayforthegoodperfectorfirst-degreepricediscriminationextractsallconsumersurplusnodeadweightloss柯孔林浙江工商大学金融学院28Themonopolistwillcontinuethiswayuntilthemarginalbuyerisnolongerwillingtopaythegood’smarginalcostQ1P1ThefirstbuyerpaysP1forQ1unitsQ2Q2P2ThesecondbuyerpaysP2forQ2-Q1unitsPerfectPriceDiscriminationQuantityPriceDUnderperfectpricediscrimination,themonopolistchargesadifferentpricetoeachbuyerMC柯孔林浙江工商大学金融学院29MarketSeparationAlessstringentrequirementwouldbetoassumethatthemonopolycanseparateitsbuyersintoafewidentifiablemarketscanfollowadifferentpricingpolicyineachmarketthird-degreepricediscriminationsetpriceaccordingtotheinverseelasticityrule,Ifthemarginalcostisthesameinallmarkets,柯孔林浙江工商大学金融学院30MarketSeparationThisimpliesthatTheprofit-maximizingpricewillbehigherinmarketswheredemandislesselastic柯孔林浙江工商大学金融学院31MarketSeparationQuantityinMarket2QuantityinMarket1Price0DDMRMRMCMCQ2*P2Q1*P1Iftwomarketsareseparate,maximumprofitsoccurbysettingdifferentpricesinthetwomarketsThemarketwiththelesselasticdemandwillbechargedthehigherprice柯孔林浙江工商大学金融学院32Third-DegreePriceDiscriminationSupposethatthedemandcurvesintwoseparatedmarketsaregivenbyQ1=24–P1Q2=24–2P2SupposethatMC=6ProfitmaximizationrequiresthatMR1=24–2Q1=6=MR2=12–Q2柯孔林浙江工商大学金融学院33Third-DegreePriceDiscriminationOptimalchoicesandpricesareQ1=9 P1=15Q2=6 P2=9Profitsforthemonopolyare

=(P1-6)Q1+(P2-6)Q2=81+18=99柯孔林浙江工商大学金融学院34Third-DegreePriceDiscriminationTheallocationalimpactofthispolicycanbeevaluatedbycalculatingthedeadweightlossesinthetwomarketsthecompetitiveoutputwouldbe18inmarket1and12inmarket2DW1=0.5(P1-MC)(18-Q1)=0.5(15-6)(18-9)=40.5DW2=0.5(P2-MC)(12-Q2)=0.5(9-6)(12-6)=9柯孔林浙江工商大学金融学院35Third-DegreePriceDiscriminationIfthismonopolywastopursueasingle-pricepolicy,itwouldusethedemandfunctionQ=Q1+Q2=48–3PSomarginalrevenuewouldbeMR=16–2Q/3Profit-maximizationoccurswhereQ=15 P=11柯孔林浙江工商大学金融学院36Third-DegreePriceDiscriminationThedeadweightlossissmallerwithonepricethanwithtwo:DW=0.5(P-MC)(30-Q)=0.5(11-6)(15)=37.5柯孔林浙江工商大学金融学院37Two-PartTariffsAlineartwo-parttariffoccurswhenbuyersmustpayafixedfeefortherighttoconsumeagoodandauniformpriceforeachunitconsumedT(q)=a+pqThemonopolist’sgoalistochooseaandptomaximizeprofits,giventhedemandfortheproduct柯孔林浙江工商大学金融学院38Two-PartTariffsOnefeasibleapproachforprofitmaximizationwouldbeforthefirmtosetp=MCandthensetaequaltotheconsumersurplusoftheleasteagerbuyerthismightnotbethemostprofitableapproach柯孔林浙江工商大学金融学院39Two-PartTariffsSupposetherearetwodifferentbuyerswiththedemandfunctionsq1=24-p1q2=24-2p2IfMC=6,onewayforthemonopolisttoimplementatwo-parttariffwouldbetosetp1=p2=MC=6q1=18 q2=12柯孔林浙江工商大学金融学院40Two-PartTariffsWiththismarginalprice,demander2obtainsconsumersurplusof36thiswouldbethemaximumentryfeethatcanbechargedwithoutcausingthisbuyertoleavethemarketThismeansthatthetwo-parttariffinthiscasewouldbeT(q)=36+6q柯孔林浙江工商大学金融学院41Two-PartTariffsItsprofitwouldbe

=R-C=T(q1)+T(q2)-AC(q1+q2)=72+6×30-6×30=72Theoptimaltariff:theoptimaltwo-parttariffinthissituationcanbecomputedbynotingthattotalprofitswithsuchatariffare

=2a+(p-MC)(q1+q2)Theentryfeeamustequaltheconsumersurplusobtainedbyperson2.

=0.5×2q2(12-p)

+(p-6)(q1+q2)=(24-2p)×(12-p)

+(p-6)(48-3p)=18p-p2Maximumprofitareobtainedwhenp=9anda=

0.5(24-2p)×(12-p)

=9,thereforetheoptimaltariffisT(q)=9+9q.柯孔林浙江工商大学金融学院42RegulationofMonopolyManyeconomistsbelievethatitisimportantforthepricesofregulatedmonopoliestoreflectmarginalcostsofproductionaccuratelyAnenforcedpolicyofmarginalcostpricingwillcauseanaturalmonopolytooperateatalossnaturalmonopoliesexhibitdecliningaveragecostsoverawiderangeofoutput柯孔林浙江工商大学金融学院43RegulationofMonopolyQuantityPriceDMRACMCBecausenaturalmonopoliesexhibitdecreasingcosts,MCfallsbelowAC

C1P1Q1AnunregulatedmonopolywillmaximizeprofitatQ1andP1C2P2Q2IfregulatorsforcethemonopolytochargeapriceofP2,thefirmwillsufferalossbecauseP2<C2柯孔林浙江工商大学金融学院44coverthelossesonthesalestolow-pricecustomersTheprofitsonthesalestohigh-pricecustomersareenoughtoRegulationofMonopolyQuantityPriceDACMCSupposethattheregulatorycommissionallowsthemonopolytochargeapriceofP1tosomeusersP1Q1C1OtherusersareofferedthelowerpriceofP2P2Q2C2柯孔林浙江工商大学金融学院45RegulationofMonopolyAnotherapproachfollowedinmanyregulatorysituationsistoallowthemonopolytochargeapriceabovemarginalcostthatissufficienttoearna“fair”rateofreturnoninvestmentifthisrate