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1、Chapter2MarketPowerECNUOrientalRealEstateCollege第一部分主要讨论垄断性行为——单一产品和多产品定价、质量选择、价格歧视、纵向控制等。这些部分较一般的讨论垄断力量的运作，即只要企业拥有一定程度的市场力量下的行为，并不要求它拥有完全的垄断地位。这里考察的大部分情况即使在存在竞争者的情况下也会出现。2.1MeasureofmarketpowerWhatismarketpower?Simply,marketpowermaybedefinedastheabilit
2、ytosetpricesabovecost,specificallyaboveincrementalcostormarginalcost,thatis,thecostofproducingoneextraunit.Insomemaening,centralquestionsofIOareIstheremarketpower?Howdofirmsacquireandmaintainmarketpower?Whataretheimplicationofmarketpower?Istherearolefor
3、publicpolicyregardingmarketpower?mmmmmMonopolypricingpmonopolypriceObjectivefunction：maxπ=R-Cfirst-ordercondition：dπ/dp=0sop-C’(D(p))=-D(p)/D’(p)Commonexpression：MR=MCLernerindex（AbbaLerner,1934）derivedfromfirst-ordercondition(elasticityrule)：L=(-MC)/=1
4、/εεisdemandelasticitywhereinmonopolyprice(positivevalue)ε=(dD/dp)*(p/D)Lernerindexcanbeusedtomeasureallkindsoffirms’marketpower.mLernerindexofmonopolyfirmpQLernerindexissimilarasrateofmarginalgrossprofit.Inmorecases,weusesimilarscoretomeasureLernerindex
5、,namelyuseunitcostreplaceMCpMCMRDMarginalgrossprofitMonopolypricemustinareawhereinε＞1Why?mpεisininverseratiowithmonopolypower(垄断势力)pqqpmMCMCqmpqmεinleftchartislowerthaninright’sMonopolyandmonopolyforceItseemsthatεismorereasonablethanmarketshareusedtodef
6、inemonopolyforce.Forexample,inthechart2.1,firminthelefthas90%marketsharewhiletherighthas100%,perfectmonopoly.So,accordingtomarketshareindex,therightfirmisclosertothepositionofmonopolyfirm,butinmonopolyforceangle,istheleft.Andεdependsonmuchfactors,someis
7、staticandothersaredynamic.Table2-1LernerindexofsomeindustriesinUSA行业谷类产品软饮料浓缩炼奶蒸馏水炒咖啡勒纳指数0.7170.5950.5930.5710.507行业奶油麦芽饮料香烟人造冰冰淇淋勒纳指数0.5000.4890.4260.3800.3322.2SourceofmarketpowerControlscarceresourceSeeksupportsofstake-holders,suchasforbiddonofmarket
8、entrySomeanti-entrystrategy(exampleofUSAairline)EconomyofscaleandscopeLearingeffectR&D2.3WelfareanalysisofmarketpowerGeneralwelfareorgeneralsurplusequalstoconsumersurplusplussupplierssurplus.WhenconsumerpriceequalstoMC,generalsur
