大型企业并购替代品生产企业的福利效应研究---基于威廉姆森福利权衡模型的扩展StudyonWelfareEffectofLargeEnterprises’M&AtoSubstituteProductionEnterprises*---BasedonExpansionofWilliamson’smodelofsocialwelfareXUChao-yangShenBinWuhanUniversityofScienceandEngineering,P.R.China,430073摘要：后股权分置改革时代的来临，企业并购重组的日益高涨，使得并购绩效日益受到社会的普遍关注。并购绩效的评价分为宏观和微观两个层次，宏观并购绩效的评价主要从并购对社会整体影响的角度进行。一般认为社会福利是个人福利和效用的汇总，而帕累托最优状态被认为是社会福利最大化的状态。本文通过对经典的威廉姆森模型的适度扩展，力图将企业在替代品市场的并购与威廉姆森福利权衡模型结合起来，对并购的宏观绩效即社会净福利进行相关分析。规模较大的企业在替代品市场的并购，往往不单纯是为了介入这一市场，而在于对这一替代品市场拥有一定的市场支配力。当企业在某个市场拥有了一定的市场支配力后，就拥有了一定的价格支配能力,提升替代品市场上的价格很可能影响原产品市场的产品需求，即引起企业原产品市场需求曲线向右上方移动，进而影响社会净福利的大小。对特定条件下社会净福利变动方向等相关问题的研究，有助于寻求增加社会福利的新途径。关键词：并购威廉姆森福利模型扩展社会净福利Abstract:Withthecomingoferaofthepostequitydivisionreform,awaveofM&AReorganizationwassetoff,whichattractedpublicconcerningonitsperformance.MacroscopicandmicroscopicconstitutestwolevelsofperformanceappraisalofM&A.ThemacroscopicappraisaltoM&Aperformanceismainlyconductedfromtheaspectofitsaffectiontothewholesociety.Oncommon,itisconsideredthatthesocialwelfareistheaggregationofindividualwelfareandutility,whileParetoOptimumisconsideredtobethemaximumofthesocialwelfare.Inthearticle,theOptimumofthemacroscopicperformancecouldbedescribedastheOptimumofthenetsocialwelfare.ThearticlegivestherelatedanalysistothenetsocialwelfarebythewayoftheexpansionofclassicalWilliamson’smodelanditscombinationwithenterprises’M&Atosubstituteproductionmarkets.Tothelargescaledcorporations’M&Ainthesubstituteproductionmarkets,itsactionisnotonlyattheaimofinterveningthemarket,butforsomemarketcontrol.Assoonasthecorporationwinsthecontrolinsomegivenmarkets,itwillpossesssomepricecontrollingpower.Theascentofthepriceinthesubstitutemarketmightaffectthedemandofthepreviousproductmarket,namelytocausethedemandcurveofthepreviousproductsmovingtothedirectionofrightandupward,thustoaffecttheamountofthesocialnetwelfare.Studyontherelatedproblemsofthe*ProjectofNationalNaturalScienceFoundationofChina(No.70772116)changingdirectionsofthenetsocialwelfareunderspecificc