壟斷競(jìng)爭(zhēng)與寡頭市場(chǎng)

ChapterCompetitionand(ChapterCompetitionand(壟斷競(jìng)爭(zhēng)與寡頭市場(chǎng)北京大學(xué)經(jīng)濟(jì)1Chapter77.1Monopolistic7.22Chapter77.1Monopolistic7.22北京大學(xué)經(jīng)濟(jì)Zhang（2007）:Chapter11，12,P322-Zhang（2007）:Chapter11，12,P322-Nicholson:Chapter19,P537-3北京大學(xué)經(jīng)濟(jì)ReadingsaboutthepartofthisChapter74北京大學(xué)經(jīng)濟(jì)Chapter74北京大學(xué)經(jīng)濟(jì)7.2.1Whatis7.2.2Quantity KinkedDemandCurveModel（折彎的需求曲線模7.2.3Price Duopoly（伯特蘭雙寡頭模型 Leaderships(價(jià)格領(lǐng)導(dǎo)者模型Chapter75北京大學(xué)經(jīng)濟(jì)Chapter75北京大學(xué)經(jīng)濟(jì)7.2.1Whatis7.2.2Quantity KinkedDemandCurveModel（折彎的需求曲線模7.2.3Price Duopoly（伯特蘭雙寡頭模型 Leaderships(價(jià)格領(lǐng)導(dǎo)者模型TheSpectrumofMarketTheSpectrumofMarket大學(xué)6京Oligopoly:AlternativeModelsofImperfectOligopoly:AlternativeModelsofImperfectMonopolyandmonopolisticDuopoly(雙寡頭廠商twofirmsinOligopoly-afew(>2)firmsinEssentialFeaturesofNatureofinteractionbetweenfirms(beyondthosecapturedinprice)isessenceoftheoriesNosingle“grandtheory”（無(wú)單一理論北京大學(xué)經(jīng)濟(jì)7WhatisAnOligopolyisamarketservedbyarelativelyfewfirms.,usuallylessthan10.DuopolyWhatisAnOligopolyisamarketservedbyarelativelyfewfirms.,usuallylessthan10.Duopoly（雙寡頭市場(chǎng)）twoTriopoly三寡頭廠商threeMultipoly多寡頭市場(chǎng)Theproductsfirmsoffercanbeeitherdifferentiated（異質(zhì)性）orhomogeneous（同質(zhì)性）.Firmsinanoligopolyareinterdependent(?存TheactionsofonefirmaffecttheprofitstheotherSothekeyfeatureofanoligopolyisthatfirms?8北京大學(xué)經(jīng)濟(jì)ExamplesofTennisBalls:Wilson,Penn,ExamplesofTennisBalls:Wilson,Penn,DunlopandCars:GM,Ford,Cereal(食品QuakerRalstonFoodKellogg,PostandGeneralMills.Airlines:AmericanandDeltawithUSAirways,NorthwestandTWAstrugglingalong.Aircraft:Boeing(+McDonnellDouglas)andLockheedMartinMobilePhone:Nokiaand北京大學(xué)經(jīng)濟(jì)9ExamplesofPCExamplesofPCoperatingcopy北京大學(xué)經(jīng)濟(jì)Oligopoly-Assumption1:ThereareOligopoly-Assumption1:Therearearelativelyfewfirms.,usuallylessthan10Eachsellerislargeenoughtoinfluenceprice,itmeanseachsellerfacesadownwardslopingdemandcurveAssumption2:firmsareTheactionsofanyonesellerinthemarketcanhavealargeimpactontheprofitsofalltheothersellers.北京大學(xué)經(jīng)濟(jì)Oligopoly-Assumption3:TheproductsOligopoly-Assumption3:Theproductsfirmsoffercanbeeitherdifferentiatedorhomogeneous.Productmaybethesamesuchasaluminumandcrudeoil。PureOligopoly productmaybedifferent,suchascopymachinesandcigarettes.Differentiatedbutcompetingproductsare北京大學(xué)經(jīng)濟(jì)Oligopoly-Assumption4:noteasyforentryandOligopoly-Assumption4:noteasyforentryandButthereareCompetitionsamongrangesfromcollusiontocutthroat北京大學(xué)經(jīng)濟(jì)Oligopoly:TraditionalCooperativeModels(合作型模型PriceLeadershipOligopoly:TraditionalCooperativeModels(合作型模型PriceLeadershipModel（價(jià)格領(lǐng)導(dǎo)模型KinkedDemandCurveModel（折彎的需求曲線模型）CournotDuopoly（古諾雙寡頭模型）BertrandDuopoly（伯特蘭雙寡頭模型）北京大學(xué)經(jīng)濟(jì)北京大學(xué)經(jīng)濟(jì)Chapter7北京大學(xué)經(jīng)濟(jì)Chapter77.2.1Whatis7.2.2QuantityKinkedDemandCurveModel（折彎的需求曲線模型7.2.3Price Duopoly（伯特蘭雙寡頭模型 Leaderships(價(jià)格領(lǐng)導(dǎo)者模型Oligopoly:TraditionalSimplestModelofOligopoly:Oligopoly:TraditionalSimplestModelofOligopoly:Assumeonlytwofirms(tolimitAssumehomogeneousNoproductSinglemarketNocompetitioninEquilibrium:Solveforoutput,priceofeach北京大學(xué)經(jīng)濟(jì)Model1（古諾模型IllustratestheprincipleModel1（古諾模型Illustratestheprincipleofmutualinterdependenceamongsellersintightlyconcentratedmarkets--evenwheresuchinterdependenceisunrecognizedbysellers.1AugustinCournot.ResearchIntotheMathematicalPrinciplesoftheTheoryofWealth,1838北京大學(xué)經(jīng)濟(jì)Cournot1.Two2.TC1=TC(qCournot1.Two2.TC1=TC(q1),HomogeneousOutputqisthe“decisionMaximizingbehaviorEverysellerknowsexactlythedemandofthemarket北京大學(xué)經(jīng)濟(jì)CournotAssumeoutputisstrategicvariable,eachCournotAssumeoutputisstrategicvariable,eachfirmchoosesoutputtomaxprofits,givenoutputlevelofcompetitorSo“FirmscompeteinFirm1:q1Firm2:q2totalquantitysuppliedisq1+marketpricewillbep(q1+totalcostfunctionsarec1(q1)and北京大學(xué)經(jīng)濟(jì)CournotModel:QuantityFirm1maximizesCournotModel:QuantityFirm1maximizesprofit,givenFirm1profit1(q1;q2)=p(q1+q2)q1–Firm1ReactionFunction”(反應(yīng)函數(shù)Whatoutputq1maximizesfirm1Givenq2(expectedorSolveforreactionfunctionq1=R(q2北京大學(xué)經(jīng)濟(jì)QuantityLetmarketinversedemandfunctionQuantityLetmarketinversedemandfunctionp(Q)=60-QQ=q1+q2Letfirms’(different)totalcostfunctionsc1(q1)=q12c2(q2)=15q2+q22北京大學(xué)經(jīng)濟(jì)QuantityCompetition:Firm1profitfunction(q;q)(60q)q21QuantityCompetition:Firm1profitfunction(q;q)(60q)q2121211So,givenq2,solveforfirm1profit-maximizing602q2q1211Firm1’sreactionfunction(bestresponse)qR(q)15111224北京大學(xué)經(jīng)濟(jì)QuantityCompetition:Firm1’s“ReactionCurve”qQuantityCompetition:Firm1’s“ReactionCurve”qR(q)15111224北京大學(xué)經(jīng)濟(jì)QuantityCompetition:Similarly,givenq1,Firm2’sprofitfunction(q;q)(60qq)q2QuantityCompetition:Similarly,givenq1,Firm2’sprofitfunction(q;q)(60qq)q2q22112222TogetFirm2’sprofit-maximizing60q151222Firm2’sreactionfunction(bestresponse)45(q)qR2214北京大學(xué)經(jīng)濟(jì)QuantityCompetition:Firm2’s“ReactionCurve”QuantityCompetition:Firm2’s“ReactionCurve”qR(q)452214北京大學(xué)經(jīng)濟(jì)QuantityCompetition:EquilibriumisaCournot-NashQuantityCompetition:EquilibriumisaCournot-NashEachfirm’soutputlevelisbestresponsetofirm’soutputStable:neitherfirmwantstochangeThus,(q1*,q2*)suchq1*=R1(q2*)q2*=北京大學(xué)經(jīng)濟(jì)QuantityCompetition:CNR(q*)15145q2R(q)** 41122 4QuantityCompetition:CNR(q*)15145q2R(q)** 41122 4Substituteforq2*to145q115q**114144q84Cournot-Nashequilibrium(q*,q*),12北京大學(xué)經(jīng)濟(jì)QuantityCompetition:Firm1’s“reactionqR(q)15QuantityCompetition:Firm1’s“reactionqR(q)15111224Firm2’s“reaction(q)45q2214北京大學(xué)經(jīng)濟(jì)QuantityCompetition:Firm1’s“reactionqR(q)1511122QuantityCompetition:Firm1’s“reactionqR(q)15111224Firm2’s“reactionqR(q)452214Cournot-Nash813,*q,1q1北京大學(xué)經(jīng)濟(jì)CournotDuopolyLetthemarket(inverse)demandp=CournotDuopolyLetthemarket(inverse)demandp=a–whereQ=+MC1=MC2=北京大學(xué)經(jīng)濟(jì)erdAnExampleoftheCournotAnExampleoftheCournotaqbqbq211 北京大學(xué)經(jīng)濟(jì)erdMR1q1a2bq1MR1MC1MR1q1a2bq1MR1MC1Firm1'sReactionac1q122Firm2'sReactionac1q212北京大學(xué)經(jīng)濟(jì)erdAnExampleoftheCournotCournotEquilibrium:q1acbq2a2cb1AnExampleoftheCournotCournotEquilibrium:q1acbq2a2cb1q222ac,aq**122(acqQCournot12acabQPCournot3北京大學(xué)經(jīng)濟(jì)qofFirm(a–(a–q*2qofFirm(qofFirm(a–(a–q*2qofFirm(a–q*(a–1北京大學(xué)經(jīng)濟(jì)q1*=q2*=(a–Firm2’sReactionq2=(a–c)/2bCournotequilibrium(q1*,q2Firm1’sReactionq1=(a–c)/2bqCournot=2(a–MonopolyoutputqCournot=2(a–Monopolyoutputwouldbe(MR=a2bqm=qm=(a–Competitiveoutputwouldbe(p=a–=qc=(a–qm<qCournot<北京大學(xué)經(jīng)濟(jì)pCournot=c+(a–MonopolypricepCournot=c+(a–Monopolypricewouldpm=c+(a–Competitivepricewouldpc=pm>pCournot>北京大學(xué)經(jīng)濟(jì)DuopolyFirm2’sCompetitiveEquilibrium(P=MC;Profit=CournotDuopolyFirm2’sCompetitiveEquilibrium(P=MC;Profit=CournotCollusiveFirm1’s(a-北京大學(xué)經(jīng)濟(jì)Forthefirm,collusionisthebestoutcomefollowedbytheCournotEquilibriumandthenthecompetitiveequilibriumKnowingpCournotandqi,wecancalculateeachfirm’smaximumi=(pCournot–KnowingpCournotandqi,wecancalculateeachfirm’smaximumi=(pCournot–c)qi=[c+(a–c)/3-c]*[(a–=(a–DuopolyprofitCournot==2(a–Monopolyprofitwould=(pm–c)qm=[c+(a–c)/2-c]*[(a–=(a–Competitiveindustryprofitwould=Hence,>Cournot>=北京大學(xué)經(jīng)濟(jì)ComparisonofCournotPriceis<ComparisonofCournotPriceis<monopolybut>perfectQuantityis>monopolybut<perfectTotalprofitis<monopolybut>perfect北京大學(xué)經(jīng)濟(jì)p北京大學(xué)經(jīng)濟(jì)QDp北京大學(xué)經(jīng)濟(jì)QDBCAD北京大學(xué)經(jīng)濟(jì)BCAD北京大學(xué)經(jīng)濟(jì)SWm<SWCour.<SWcFromPCtoDuolopy,?SW=-FromDuolopyto?SW=-北京大學(xué)經(jīng)濟(jì)(a–2(a–(a–c北京大學(xué)經(jīng)濟(jì)(a–2(a–(a–c+(a–c+(a–c(a–2(a–00.5(a–0.5(a–0.5(a–CSm++CS(PS=(a–<2(a–<(a–c+(a–(a–<2(a–<(a–c+(a–(a–0.5(a–>c+(a–c)/32(a–c)2/9b0.5(a–CSCour.+>c00.5(a–>><<CSm+<<CS(PS=北京大學(xué)經(jīng)濟(jì)OutlinesofToday’s北京大學(xué)OutlinesofToday’s北京大學(xué)經(jīng)濟(jì)WhatisQuantity Duopoly（古諾雙寡頭模型StackelbergDuopoly（斯泰克伯格雙寡頭vonStackelbergModel:Onefirm(largervonStackelbergModel:Onefirm(largerfirm)movesThen“followerfirms”BothconsiderreactionsofCancompeteQuantity--vonStackelbergPrice--Priceleadership北京大學(xué)經(jīng)濟(jì)ThevonStackelbergModel(斯泰克伯格模型OutputsarestrategicFirmThevonStackelbergModel(斯泰克伯格模型OutputsarestrategicFirm1leaderfirm（領(lǐng)導(dǎo)者廠商）choosesq1firstFirm2follower（跟隨著廠商）thenreactsLeaderanticipatesreactionoffollowerWhatareprices,outputs,Isthereafirstmoveradvantage(先動(dòng)優(yōu)勢(shì)北京大學(xué)經(jīng)濟(jì)ThevonStackelbergFollowerfirmwillchooseq2tomaximizeprofit,givenleaderfirmq1ThevonStackelbergFollowerfirmwillchooseq2tomaximizeprofit,givenleaderfirmq1(C-Nassumption)Thus,followerreactionfunction:q2=Leaderfirm(1)anticipatesfollowerfirm’sreactionfunction,sochoosesq1tomaxS(q)=+R(q)]–c(q11121111北京大學(xué)經(jīng)濟(jì)VonStackelbe