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81Vol.8No.11999SYSTEMSENGINEERING-THEORYMETHODOLOGYAPPLICATIONS1999(,200052),CournotBertrand,,19988271,90,,,?,,[15],Cournot,:(1):(2)Cournot,,,CournotBertrand,,,,,,,,,2,(A,B,C),,©1994-2006ChinaAcademicJournalElectronicPublishingHouse.Allrightsreserved.(),(F),,,,b,:0b1,Pi=1-Qi-bnj=1,jiQj(1):i,j;nAB(m),m(),,m,C,,A,B,C:(1)ABm,(2)mC;Cm1nc=1nc=2nm=1Pm(1,1),Pc(1,1)Pm(1,2),Pc(1,2,)-fnm=2Pm(2,1),Pc(2,1)Pm(2,2),Pc(2,2)-f:nmC;Pm(1,1)mC()CF,,,fc=0,mC,13CournotBertrand(f),2,fPk(1,1,1)=f4,,fPA(2,1,1)-Pk(1,1,1)=f12CournotBertrandPk(1,1)k=m,C1ö(2+b)2(1-b)ö(1+b)(2-b)2Pk(1,1,1)k=A,B,C1ö(2+2b)2(1-b)(1+b)ö4(1+2b)Pm(2,1)=Pc(1,2)(1+b)(b-2)2ö2(b2-2b-2)2(1-b)(2+3b)2ö2(1+2b)(b2-2b-2)2Pk(2,2)k=m,C2(1+b)ö(2+4b)2(1-b)(1+b)ö(2+6b)Pc(2,1)=Pm(1,2)1ö(b2-2b-2)2(1-b)(1+b)3ö(1+2b)(b2-2b-2)2PA(2,1,1)(1+b)(b-2)2ö2(b2-3b-2)2(1-b2)(2+5b)2ö2(1+3b)(b2+5b+2)2Pk(1,1,1)PA(2,1,1)A,B,C(2,1,1)3.1Cournotf2=Pc(2,2)-Pc(2,1),2Cournot,0b1,:f1f2f4911999©1994-2006ChinaAcademicJournalElectronicPublishingHouse.Allrightsreserved.(nm=2.nc=2);f1f2ff4,Nash(nm=2,nc=1):AB:(nm=1,nc=1),Pm(1,1)2Pk(1,1,1);(nm=2,nc=1),Pm(2,1)2Pk(1,1,1);(nm=2,nc=2),Pm(2,2)2Pk(1,1,1)((nm=1,nc=2)(nm=2,nc=1),,),(nm=2,nc=2),:Pm(2,2)2Pk(1,1,1),2Cournot,0b1,Pm(2,2)2Pk(1,1,1)(nm=2,nc=1),2,Pm(2,1)2Pk(1,1,1),0b0.55,:1Cournot,(f1f2ff40b0.55),f1,f2,f4b;(nm=2,nc=1),,3.2Bertrandf3=Pm(2,1)-Pm(1,1),2Bertrand,b:0b0.39,0f1f2f3f4;0.39b0.78,0f2f1f3f4;0.78b1,0f2f3f1f4,1Nash:0b0.39,0f1ff2f4,Nash(nm=2,nc=2);0b0.39,0f1f2ff4,Nash(nm=2,nc=1);0.39b0.92,f1ff4,Nash(nm=2,nc=1);0.92b1,f1ff4,Nash(nm=1,nc=1):AB3.1,(nm=2,nc=2),Pm(2,2)2Pk(1,1,1),2Bertrand,0b1,Pm(2,2)2Pk(1,1,1)(nm=2,nc=1),2,Pm(2,1)2P(1,1,1),0b1,(nm=1,nc=1),Pm(1,1)2Pk(1,1,1)0.71b1BertrandNash,2Bertrand,(f1f2ff40b0.39)(f1ff40.39b0.92)(f1ff40.92b1),f1,f2,f4b;(nm=2,nc=1),(nm=1,nc=1)312,BertrrandCournot,Cournot0219991©1994-2006ChinaAcademicJournalElectronicPublishingHouse.Allrightsreserved.(1),:ni=1Ui-1ni=1piqi,n:ni=1piqi-ni=1cqif,,NW=ni=1Ui-ni=1piqi+ni=1piqi-ni=1cqi-f=ni=1Ui-fWni=1Ui,,CournotBertrand(3)3CournotBertrandW(1,1)(3+b)ö(2+b)2(3-2b)ö(4-3b2+b3)W(1,1,1)3(3+2b)ö8(1+b)23(3+2b-b2)ö(8+16b)W(2,1)(18+8b-13b2+3b3)ö4(b2-2b-2)2(11+30b+18b2-4b3-b4)ö4(1+2b)(b2-2b-2)2W(2,2)(3+5b)ö2(1+2b)2(5+6b+b2)ö(2+6b)WP4.1Cournot(nm=1,nc=1),,W(1,1)W(1,1,1),3CournotW,0b1,,(nm=2,nc=1)W(2,1)W(1,1,1),0b1,(nm=2,nc=2),W(2,2)-fW(1,1,1)f,f3.1:f1ff2f4f=f1,0b0.26;f=f2,0b0.234Cournot,:f1ff2f4,0bbmax,bmaxf,W(2,2)-f=W(1,1,1):(nm=2,nc=2)4.2Bertrand4.1,(nm=1,nc=1),,W(1,1)W(1,1,1),3BertrandW,0.71b1,(nm=2,nc=1),W(2,1)W(1,1,1),0b1,(nm=2,nc=2),0f1ff2f4,W(2,2)-121999©1994-2006ChinaAcademicJournalElectronicPublishingHouse.Allrightsreserved.(1,1,1)0b15Bertrand,:(0b0.39f1ff2f4)(0.92b1f1ff4),f1,f2,f4b,(nm=2,nc=2)(nm=1,nc=1)Cournot,:6Cournot,,,Bertrand,:7Bertrand,,0.92b1f1ff4,m,,,5,,,,,,,,,,,,,,90,(nn=2,nc=1);,,,,,,,,,,[1],ZhangA..,1994,3(3):2532[2],..,1997,6(3):17[3],,..,1997,6(4):1014[4]..,1998,32(3):4852[5]..,1996.(26)2219991©1994-2006ChinaAcademicJournalElectronicPublishingHouse.Allrightsreserved.[1]ArrowKJ.Uncertaintyandthewelfareeconomicsofmedicalcare.TheAmericanEconomicReview,1963,53:941973[2]EllisRP,McguireTG.Supply2sideanddemand2sidecostsharinginhealthcare.JournalofEconomicsPerspectives,1993,7:135154[3]Hans2WernerS.Economicdecisionunderucertain.North2HollandPublishingCompany,1983.[4]KwonS.Paymentsystemsforprovidersinhealthinsurancemarkets,TheJournalofRiskandInsurance,1997,64:155173[5]ShermanF,AllenCG,MironS.Theeconomicsofhealthandhealthcare.MacmillanPublishingCompany,1993.HowtoPreventtheAdverseSelectioninHealthInsuranceShenSiweiLiSongtao(ManagementSchoolofShanghaiJiaotongUniversity,Shanghai200052)YuZiyou(InstituteofFinanceandInsuranceofShanghaiFinanceUniversity,Shanghai200030)AbstractInthisstudy,theanothersinvestigatetheadverseselectioninhealthinsurancefromthedemandside.Underdifferentinsurancesystem,thisproblemcanbesolvedbywayofself2selectionmechanismdesigning.Keywords:agent2princopleself2selectionmechanismadverceselection(22)[6]FarrellJ,ShapiroC.Horizontalmerger:anequilibriumanalysis.TheAmericanEconomicReview,1990,80(1):107126AnalysisofMotivesandResultsofAdvantage-complementaryMergerWengYiqunChenHongminCaiLaixin(ManagementSchoolofShanghaiJiaotongUniversity,Shanghai200052)AbstractThispaperisconcernedwiththechangeoffirm’sprofitandsocialwelfaredur2ingthemergerunderaconditionofinhomogeneousgoodsandoligopoly.Bythehypothesisofuncooperativeperfectinformationstaticgamemodel,thecharacteristicsofmarketandgoodswithwhichthefirmcanimproveitsprofitthroughmergerisdiscussedunderCournotoligopolymodelandBertrandoligopolymodel.Improvingthefirm’sprofitcanbeexplainedasanincentiveforadvantage2complementarymerger.Thechangeofwelfarein2fluencedbythemergerisalsodiscussedinthispaper.Fromtheviewofmaximizingglog2balsocialwelfare,adviceisalsogiventore