Uni案例：伯爾克造紙公司西方造紙公司西方造紙公司埃里造紙4804304322801202800.6=1685230Unit6:MarketStructureandPerfectCompetitionMarketStructureandDegreeofCompetitionPerfectCompetitionShort-RunAnalysisofaPerfectlyCompetitiveFirmLong-RunAnalysisofaPerfectlyCompetitiveFirmGeneralEquilibriumofPerfectCompetitionMarketStructureandDegreeofCompetitionAMarketconsistsofalltheactualandpotentialbuyersandsellersofaparticularproduct.MarketStructurereferstothecompetitiveenvironmentinwhichthebuyersandsellersoftheproductoperate.FourTypesofMarketStructurePerfectCompetitionMonopolisticCompetitionOligopolyMonopolyImperfectCompetitionDegreeofCompetitionPerfectCompetitionistheformofmarketorganizationinwhich(1)therearemanybuyersandsellersofaproduct,eachtoosmalltoaffectthepriceoftheproduct;(2)theproductishomogeneous;(3)thereisperfectmobilityofresources;and(4)economicagentshaveperfectknowledgeofmarketcondition.Monopolyistheformofmarketorganizationinwhich:asinglefirmsellsaproductforwhichtherearenoclosesubstitutes.Entryintotheindustryisverydifficultorimpossible.MonopolisticCompetitionreferstothecasewhereTherearemanysellersofadifferentiatedproductandEntryintoorexitfromtheindustryisrathereasyinthelongrun.OligopolyisthecasewhereTherearefewsellersofahomogeneousordifferentiatedproduct;Whileentryintotheindustryispossibly,itisnoteasy(asevidencedbythesmallnumberoffirmintheindustry).Underperfectcompetition,thefirmisapricetakerMarketOneFirmq(unit)Q(104unit)p=constantFirm’sbehaviorsunderperfectcompetitionMax=TRTC,thefirstordercondition:ddQ=d(TR)dQ

d(TC)dQ=0;orMR=MC;sinceTR=pQso,MR=pandp=MCconstantShort-RunsupplycurveofafirmunderperfectcompetitionP=MCiSi=Si(p)=MC-1(p);Si(p)=P>ATC;>0,Si(p)>0P<ATC;<0,P>AVC,Si(p)>0P<AVC,Si(p)=0消費(fèi):pQTFCTVC>-TFC停產(chǎn):pQTFCTVC<-TFCShort-RunsupplycurveMC=Si(p)ATCAVCpQShort-Runmarketsupplycurve

Firm1Firm2MarketS1S2SSLong-RunAnalysisofaPerfectlyCompetitiveLACMCFirmMarketPositiveprofitMorefirmsenterthemarket

PerfectEntryLong-RunAnalysisofaPerfectlyCompetitiveMCLACLossesMorefirmsleaveInlong-run:mostefficientfirmsremainwithlowestcostandzeroeconomicprofitMCLACpP=MC=LAC=MRGeneralEquilibriummax{Ui(qi)}max{p(q+q)j}s.t.pqi=pwi+Tij{p(q+q)j}Di=qi(p)Sj=Sj(p)D(p)=Di=qi(p)S(p)=Sj=Sj(p)D(p)=S(p)+W練習(xí)1，某種產(chǎn)品的市場(chǎng)需求函數(shù)為D(p)=300020p，符合完全競(jìng)爭(zhēng)的假設(shè)，共有100個(gè)同樣的企業(yè)在該行業(yè)消費(fèi)，每個(gè)企業(yè)的本錢函數(shù)為Ci=30qi+qi2+300求：〔1〕每個(gè)企業(yè)的供應(yīng)曲線〔短期〕；〔2〕市場(chǎng)的供應(yīng)曲線；〔3〕市場(chǎng)供求平衡時(shí)的價(jià)錢與供求量。2，資料同上題，求長(zhǎng)期市場(chǎng)運(yùn)作的結(jié)果〔假定企業(yè)的消費(fèi)本錢不變〕，該由多少個(gè)企業(yè)進(jìn)展消費(fèi)？解1：〔1〕由完全競(jìng)爭(zhēng)的假設(shè)，p=MCi=30+2qiorqi=si=p/2–15(每個(gè)企業(yè)的供應(yīng)曲線〔2〕市場(chǎng)的供應(yīng)曲線：S=100si=50p–1500;〔3〕市場(chǎng)供求平衡時(shí)：D=S;3000–20p=50p–1500;p=64.29;Q=1714;qi=17.14每個(gè)企業(yè)的利潤(rùn)：=17.1464.29–(3017.14+17.142+300)=–6.08解2:長(zhǎng)期運(yùn)作的結(jié)果是:p=MCi=ATCmin;30+2qi=30+qi+300/qi;qi=17.32;p=64.64;Q=1707.2;n=98.Unit7:MarketStructure:Monopoly&MonopolisticCompetitionMonopolyComparisonofMonopolyandPerfectCompetitionMonopolisticCompetitionSourcesofMonopolyAfirmcontrolstheentiresupplyofrawmaterialsrequiredtoproducetheproduct;Afirmownsapatentorcopyright;Naturalmonopoly:Governmentfranchise.Thecomparativedegreeofmonopoly行業(yè)最大的廠商銷售額(百分美圓)航天波音公司〔美國(guó)〕56154商業(yè)銀行美國(guó)公司銀行〔美國(guó)〕50777飲料百事可樂〔美國(guó)〕22348建筑資料、玻璃SAINT-GOBAIN(法國(guó)〕19818化工杜邦公司〔美國(guó)〕39130計(jì)算機(jī)效力與軟件電子數(shù)據(jù)系統(tǒng)〔美國(guó)〕16891計(jì)算機(jī)，辦公室設(shè)備IBM〔美國(guó)〕81667電子電氣設(shè)備通用電氣公司〔美國(guó)〕100469文娛沃特·迪斯尼〔美國(guó)〕22976食品雀巢公司〔瑞士〕49504普通商業(yè)沃爾瑪〔美國(guó)〕208保險(xiǎn)〔人壽〕日本生活〔日本〕66300金屬日本鋼鐵〔日本〕21508廠商的規(guī)模——某些行業(yè)中的世界最大廠商廠商的規(guī)?！承┬袠I(yè)中的世界最大廠商〔續(xù)〕行業(yè)最大的廠商銷售額(百分美圓)汽車及零件通用汽車公司〔美國(guó)〕161315石油?？松裁绹?guó)〕100697藥品默克〔美國(guó)〕26989橡膠橋石〔日本〕17107證券美林〔美國(guó)〕35853日化P&G〔美國(guó)〕37154專業(yè)零售HOMEDEPOT〔美國(guó)〕30219電信日本電報(bào)〔日本〕76119煙草菲利浦·莫里斯〔美國(guó)〕57813貿(mào)易三井物產(chǎn)〔日本〕109373公用事業(yè)、東京電力〔日本〕39808零售INGRAMMICRO22034資料來(lái)源：FORTUNEAugust2,1999行業(yè)集中程度1.集中率就是最大的4,8,20或50家廠商市場(chǎng)占有率之和。四廠商集中率(4CR)為0.8就是最大的四家廠商占有所在行業(yè)銷售量的80%。2.赫芬達(dá)爾-赫希曼指數(shù)(HHI):HHI=Si2,就是該行業(yè)中所廠商的市場(chǎng)占有率的平方和。假設(shè)行業(yè)內(nèi)存在無(wú)數(shù)小廠商，該指數(shù)接近為零。當(dāng)一個(gè)行業(yè)接近于壟斷時(shí)，HHI接近于1。衡量市場(chǎng)集中程度時(shí)應(yīng)留意：全球市場(chǎng)；國(guó)家、地域和本地市場(chǎng)；行業(yè)的定義和產(chǎn)品的種類美國(guó)某些行業(yè)的四廠集中率與HHI指數(shù)行業(yè)C4HHI書籍出版13102瓶裝與罐裝飲料14190早餐麥片食品86N/A香煙872564寵物食品521167電子計(jì)算設(shè)備43793液體奶品16151速凍食品與蔬菜27306家用冰箱和冷凍器942745報(bào)紙22期刊20175婦女服裝624肥皂及其他洗滌品601306美國(guó)行業(yè)的集中程度四廠商集中度赫芬達(dá)爾-赫希曼指數(shù)市場(chǎng)構(gòu)造——美國(guó)情況Short-RunPriceandOutputDeterminationbyaMonopolistACMCDDMRQ*P*=R(Q)C(Q)thefirstordercondition:R/Q=C/Q,orMR=MCLong-RunPriceandOutputDeterminationbyaMonopolyLACLMCDDMRQ*P*ComparisonofMonopolyandPerfectCompetitionMCDDpmpcQmQcTransferfromCStoprofitDeadweightloss例子：某種產(chǎn)品的市場(chǎng)需求函數(shù)為D(p)=300020p〔1〕符合完全競(jìng)爭(zhēng)的假設(shè)，共有100個(gè)同樣的企業(yè)在該行業(yè)消費(fèi)，每個(gè)企業(yè)的本錢函數(shù)為Ci=30qi+qi2+300求：市場(chǎng)供求平衡時(shí)的價(jià)錢與供求量；〔2〕由一個(gè)企業(yè)壟斷消費(fèi)，其本錢函數(shù)為C=30Q+0.01Q2+30,000,求企業(yè)為利潤(rùn)最大化作出的決策〔售價(jià)與產(chǎn)銷量〕；〔3〕試比較兩種市場(chǎng)構(gòu)造的效率差別。例子D(p)=3,00020pMR=150-0.1QMC=30+0.02Q10064.291,0001714②①④

⑤例子ElasticityofDemandandPriceMarkup

Lerner’sDegreeofMonopolyPower

L=(p-MC)/p=-1/EdP*-MCARMRMCP*P*-MCARMRMCP*壟斷競(jìng)爭(zhēng)壟斷競(jìng)爭(zhēng)的市場(chǎng)構(gòu)造很多買主和賣主進(jìn)出行業(yè)很容易產(chǎn)品差別化歷史背景瓊·羅賓遜,不完全競(jìng)爭(zhēng)經(jīng)濟(jì)學(xué),1933愛德華·張伯倫,壟斷競(jìng)爭(zhēng)實(shí)際,1933ProductDifferentiationAmongGasStations產(chǎn)品差別差別化：