昆明理工大学MBA中级微观第25章讲义垄断行为

ChapterTwenty-FiveMonopolyBehavior垄断行为HowShouldaMonopolyPrice?Sofaramonopolyhasbeenthoughtofasafirmwhichhastosellitsproductatthesamepricetoeverycustomer.Thisisuniformpricing.Canprice-discrimination（差别定价）earnamonopolyhigherprofits?StructureFirst-degreepricediscriminationSecond-degreepricediscriminationThird-degreepricediscriminationBundlingTwo-parttariffTypesofPriceDiscrimination1st-degree:Eachoutputunitissoldatadifferentprice.Pricesmaydifferacrossbuyers.2nd-degree:Thepricepaidbyabuyercanvarywiththequantitydemandedbythebuyer.Butallcustomersfacethesamepriceschedule.E.g.bulk-buyingdiscounts.TypesofPriceDiscrimination3rd-degree:Pricepaidbybuyersinagivengroupisthesameforallunitspurchased.Butpricemaydifferacrossbuyergroups.E.g.,seniorcitizenandstudentdiscountsvs.nodiscountsformiddle-agedpersons.First-degreePriceDiscriminationEachoutputunitissoldatadifferentprice.Pricemaydifferacrossbuyers.Itrequiresthatthemonopolistcandiscoverthebuyerwiththehighestvaluationofitsproduct,thebuyerwiththenexthighestvaluation,andsoon.First-degreePriceDiscriminationp(y)y$/outputunitMC(y)ypy()Sellthethunitfor$ypy().First-degreePriceDiscriminationp(y)y$/outputunitMC(y)ypy()ypy()Sellthethunitfor$Lateronsellthethunitfor$ypy().ypy().First-degreePriceDiscriminationp(y)y$/outputunitMC(y)ypy()yypy()py()Sellthethunitfor$Lateronsellthethunitfor$Finallysellthethunitformarginalcost,$ypy().ypy().ypy().First-degreePriceDiscriminationp(y)y$/outputunitMC(y)ypy()yypy()py()Thegainstothemonopolistonthesetradesare:andzero.pyMCypyMCy()(),()()Theconsumers’gainsarezero.First-degreePriceDiscriminationp(y)y$/outputunitMC(y)ySothesumofthegainstothemonopolistonalltradesisthemaximumpossibletotalgains-to-trade.PSFirst-degreePriceDiscriminationp(y)y$/outputunitMC(y)yThemonopolistgetsthemaximumpossiblegainsfromtrade.PSFirst-degreepricediscriminationisPareto-efficient.First-degreePriceDiscriminationFirst-degreepricediscriminationgivesamonopolistallofthepossiblegains-to-trade,leavesthebuyerswithzerosurplus,andsuppliestheefficientamountofoutput.Examplesof1st-degreePriceDiscriminationAuctionofantiqueCarsalesFinancialaidinuniversitiesMaynotbepractical–donotknowwillingnesstopay–toocostlyNon-linearpricing–Unitpricedependsonquantitypurchased–BulkdiscountSetting–Asellerdoesnotknowthewillingnesstopaybyeachindividualbuyer–Consumer’smarginalwillingnesstopaydeclineswithquantitySecond-degreePriceDiscriminationSettingauniformpriceisnotoptimal–Toohighapricewouldlosehighvolumeconsumer.–Toolowapricewouldlostrevenuefromlowvolumeconsumer.–Cokeexample.Mechanism：SetpricefordifferentvolumestoletconsumersidentifythemselvesSecond-degreePriceDiscriminationTwoconsumers–Person1haslowwillingness-to-pay–Person1hashighwillingness-to-payAssume0MCAnExampleAquantity$/outputunitx10x20CBChargeAforx10hopingtogetperson1ChargeA+B+Cforx20hopingtogetperson2Butperson2isbetteroffbuyingx10andreceivingacs=BFailtoletconsumersself-selectthemselvesProfit=2ACanalternativelychargeA+Cforx20toidentifyperson2profit=2A+CSecond-degreePriceDiscriminationAquantity$/outputunitx10x20CBReducex10soAisreducedbyalittlebutCcanbeincreasedbyalot。Persons1and2arestillidentifiedProfitishigherSecond-degreePriceDiscriminationAquantity$/outputunitMC(y)x1mx20CBProfitismaximizedatx1mSecond-degreePriceDiscrimination2nd-degreediscriminationcanalsooccurinthedimensionofqualityDifferentpricesfordifferentseatsinatheaterDifferentpricesforeconomyclassvs.businessclassseatsinairplanesSecond-degreePriceDiscriminationThird-degreePriceDiscriminationPricepaidbybuyersinagivengroupisthesameforallunitspurchased.Butpricemaydifferacrossbuyergroups.Qualityofgoodsisthesameacrossgroups.Canidentifygroupsbutnofurtheridentificationwithinthatgroup.Third-degreePriceDiscriminationAmonopolistmanipulatesmarketpricebyalteringthequantityofproductsuppliedtothatmarket.Sothequestion“Whatdiscriminatorypriceswillthemonopolistset,oneforeachgroup?”isreallythequestion“Howmanyunitsofproductwillthemonopolistsupplytoeachgroup?”Third-degreePriceDiscriminationTwomarkets,1and2.y1isthequantitysuppliedtomarket1.Market1’sinversedemandfunctionisp1(y1).y2isthequantitysuppliedtomarket2.Market2’sinversedemandfunctionisp2(y2).Third-degreePriceDiscriminationForgivensupplylevelsy1andy2thefirm’sprofitisWhatvaluesofy1andy2maximizeprofit?(,)()()().yypyypyycyy1211122212Third-degreePriceDiscrimination(,)()()().yypyypyycyy1211122212Theprofit-maximizationconditionsareyypyycyyyyyyy1111112121210()()()()yypyycyyyyyyy2222212121220()()()()Third-degreePriceDiscrimination()yyy1211()yyy1221andsotheprofit-maximizationconditionsareypyycyyyy11111212()()()andypyycyyyy22221212()()().Third-degreePriceDiscriminationypyyypyycyyyy111122221212()()()()MR1(y1)=MR2(y2)saysthattheallocationy1,y2maximizestherevenuefromsellingy1+y2outputunits.E.g.ifMR1(y1)MR2(y2)thenanoutputunitshouldbemovedfrommarket2tomarket1toincreasetotalrevenue.Th