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1、信息不对称AsymmetricInformation(卫生经济学)逆向选择AdverseSelection逆向选择将会导致某些人购买医疗保险Adverseselectionwouldresultinabiasedsampleofthosethatpurchasehealthinsurance更多的高风险个人将购买保险Predominantly,morehighriskindividualswouldpurchaseinsurance“柠檬”法则TheLemonsPrinciple高风险的人驱逐低风险的人直至市场不存在Thebaddrivesouttheg
2、ooduntilnomarketisleft柠檬法则TheLemonsPrincipleAkerlof(1970)用信息不对称的观点分析二手车市场Akerlof(1970)usedtheideaofasymmetricinformationtoanalyzetheusedcarmarket二手车的质量千差万别Usedcarsavailableforsalevaryinquality对称不信息Asymmetricinformation卖者比买者更了解车子的质量Thesellersknowbetterthetruequalityoftheircarsthan
3、thebuyers有9辆车供出售Thereare9carsforsale质量(Q)=0,¼,½,¾,1,1¼,1½,1¾,2卖者了解每辆车的质量Seller(owner)knowseachcar’squality买者只知道质量的分布Buyeronlyknowsthedistributionofquality柠檬法则TheLemonsPrinciple卖者的保留价值是$1000xQSellerhasareservevalue=$1000xQ买者的保留价值是$1,500xQBuyerhasareservevalue=$1,500xQ雇佣一个拍卖人报价。拍卖人
4、找到一个需求量等于供给量的价格就成交Anauctioneerishiredtocalloutprices.Salestakeplacewhentheauctioneerfindsapricethatmakesquantitydemandedequalquantitysupplied我们现在进行这个拍卖游戏Wedothesalesgametogetherinclass柠檬法则TheLemonsPrinciple如果信息对称，买者和卖者都不清楚具体的质量，他们只知道车子的平均质量，此时二手车市场能否存在？市场价格是多少？Ifinformationhadbee
5、nsymmetric,bothownersandbuyerswereuncertainofthequality,theyonlyknowtheaveragequalityofcars,thenisthereamarketfortheusedcars?Whatwouldbethemarketprice?柠檬法则的应用：医疗保险ApplicationofTheLemonsPrinciple:HealthInsurance信息不对称Informationasymmetry潜在的参保者比医疗保险公司更了解自己将来可能的医疗保健支出Thepotentialinsu
6、redpersonknowsmoreabouther(his)expectedhealthexpendituresinthecomingperiodthandoestheinsurancecompany.具体地讲Morespecifically参保者知道自己将来的医疗费用（类似于二手车的车主）Insuredknowsher(his)futureexpenditureexactly(similartotheownerofthecars)保险公司只了解所有参保者的医疗费用的分布（类似于买车的人）Insurancecompanyknowsonlythedist
7、ributionofexpendituresforallinsuredpersons(similartothebuyerofthecars)柠檬法则的应用：医疗保险ApplicationofTheLemonsPrinciple:HealthInsurance医疗保险市场有5个人Thereare5personsinhealthinsurancemarket预期的医疗费用＝0,¼,½,¾,1Expectedexpenditure=0,¼,½,¾,1平均医疗费用＝½Averageexpenditure=½我们再做一个游戏看医疗保险市场是否存在Wedothega
8、meagaininclasstocheckifthereishealthinsu
