范里安微观经济学现代观点 课件第36章.ppt

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1、ChapterThirty-SixAsymmetricInformationInformationinCompetitiveMarketsInpurelycompetitivemarketsallagentsarefullyinformedabouttradedcommoditiesandotheraspectsofthemarket.Whataboutmarketsformedicalservices,orinsurance,orusedcars?AsymmetricInformationinMarketsAdoct

2、orknowsmoreaboutmedicalservicesthandoesthebuyer.Aninsurancebuyerknowsmoreabouthisriskinessthandoestheseller.Ausedcar’sownerknowsmoreaboutitthandoesapotentialbuyer.AsymmetricInformationinMarketsMarketswithonesideortheotherimperfectlyinformedaremarketswithimperfec

3、tinformation.Imperfectlyinformedmarketswithonesidebetterinformedthantheotheraremarketswithasymmetricinformation.AsymmetricInformationinMarketsInwhatwayscanasymmetricinformationaffectthefunctioningofamarket?Fourapplicationswillbeconsidered:adverseselectionsignali

4、ngmoralhazardincentivescontracting.AdverseSelectionConsiderausedcarmarket.Twotypesofcars;“lemons”and“peaches”.Eachlemonsellerwillaccept$1,000;abuyerwillpayatmost$1,200.Eachpeachsellerwillaccept$2,000;abuyerwillpayatmost$2,400.AdverseSelectionIfeverybuyercantella

5、peachfromalemon,thenlemonssellforbetween$1,000and$1,200,andpeachessellforbetween$2,000and$2,400.Gains-to-tradearegeneratedwhenbuyersarewellinformed.AdverseSelectionSupposenobuyercantellapeachfromalemonbeforebuying.Whatisthemostabuyerwillpayforanycar?AdverseSelec

6、tionLetqbethefractionofpeaches.1-qisthefractionoflemons.ExpectedvaluetoabuyerofanycarisatmostAdverseSelectionSupposeEV>$2000.Everysellercannegotiateapricebetween$2000and$EV(nomatterifthecarisalemonorapeach).Allsellersgainfrombeinginthemarket.AdverseSelectionSupp

7、oseEV<$2000.Apeachsellercannotnegotiateapriceabove$2000andwillexitthemarket.Soallbuyersknowthatremainingsellersownlemonsonly.Buyerswillpayatmost$1200andonlylemonsaresold.AdverseSelectionHence“toomany”lemons“crowdout”thepeachesfromthemarket.Gains-to-tradearereduc

8、edsincenopeachesaretraded.Thepresenceofthelemonsinflictsanexternalcostonbuyersandpeachowners.AdverseSelectionHowmanylemonscanbeinthemarketwithoutcrowdingoutthepeaches