信息不對稱AsymmetricInformation(衛(wèi)生經(jīng)濟(jì)學(xué))課件

信息不對稱AsymmetricInformation信息問題InformationProblems患者——缺乏信息，也沒有能力識別質(zhì)量Patients—lackofinformationandinabilitytodiscernquality保險方——缺乏參保者的健康狀況信息Insurers—lackofinformationaboutindividual’shealthbackground逆向選擇Adverseselection假設(shè)有10個低風(fēng)險的人和10個高風(fēng)險的人，高風(fēng)險的人預(yù)期的醫(yī)療保健費是1000美元，低風(fēng)險的人預(yù)期的醫(yī)療保健費是100美元。醫(yī)療保險費的確定基于平均的預(yù)期醫(yī)療保健費，也就是550美元Supposethereare10lowriskpeopleand10highriskpeople,thehighriskpeople’sexpectedhealthcareexpenditurewillbe$1000,thelowrisk’swillbe$100.Thehealthinsurancepremiumisbasedonaverageexpectedexpenditure,whichis$550.

信息不對稱AsymmetricInformation信息1逆向選擇AdverseSelection保險公司無法區(qū)分風(fēng)險高和風(fēng)險低的人。保險費只反映了兩類人的平均風(fēng)險。因此高風(fēng)險的人將購買保險，因為此時的保險費低于完全依照他們的風(fēng)險確定的保險費。而低風(fēng)險的人可能不會購買保險，因為此時的保險費高于完全依照他們的風(fēng)險確定的保險費。Theinsurancecompanyisunabletodistinguishbetweenhighandlowrisks.Theinsurancepremiumonlyreflectstheaverageriskofthetwogroups.Then,thehighriskgroupwillpurchaseinsurancesinceapremiumbasedontheaverageriskislowerthanapremiumbasedsolelyontheirownrisk.Thelowriskindividualsmaynotpurchaseinsurancesinceapremiumbasedontheaveragewouldbegreaterthantheirownrisk-basedpremium.逆向選擇AdverseSelection保險公司無法區(qū)分2逆向選擇AdverseSelection逆向選擇將會導(dǎo)致某些人購買醫(yī)療保險Adverseselectionwouldresultinabiasedsampleofthosethatpurchasehealthinsurance更多的高風(fēng)險個人將購買保險Predominantly,morehighriskindividualswouldpurchaseinsurance“檸檬”法則TheLemonsPrinciple高風(fēng)險的人驅(qū)逐低風(fēng)險的人直至市場不存在Thebaddrivesoutthegooduntilnomarketisleft逆向選擇AdverseSelection逆向選擇將會導(dǎo)致3檸檬法則TheLemonsPrincipleAkerlof(1970)用信息不對稱的觀點分析二手車市場Akerlof(1970)usedtheideaofasymmetricinformationtoanalyzetheusedcarmarket二手車的質(zhì)量千差萬別Usedcarsavailableforsalevaryinquality對稱不信息Asymmetricinformation賣者比買者更了解車子的質(zhì)量Thesellersknowbetterthetruequalityoftheircarsthanthebuyers有9輛車供出售Thereare9carsforsale質(zhì)量(Q)=0,?,?,?,1,1?,1?,1?,2賣者了解每輛車的質(zhì)量Seller(owner)knowseachcar’squality買者只知道質(zhì)量的分布Buyeronlyknowsthedistributionofquality檸檬法則TheLemonsPrincipleAkerl4檸檬法則TheLemonsPrinciple賣者的保留價值是$1000xQ

Sellerhasareservevalue=$1000xQ買者的保留價值是$1,500xQ

Buyerhasareservevalue=$1,500xQ雇傭一個拍賣人報價。拍賣人找到一個需求量等于供給量的價格就成交Anauctioneerishiredtocalloutprices.Salestakeplacewhentheauctioneerfindsapricethatmakesquantitydemandedequalquantitysupplied我們現(xiàn)在進(jìn)行這個拍賣游戲Wedothesalesgametogetherinclass檸檬法則TheLemonsPrinciple賣者的保留5檸檬法則TheLemonsPrinciple如果信息對稱，買者和賣者都不清楚具體的質(zhì)量，他們只知道車子的平均質(zhì)量，此時二手車市場能否存在？市場價格是多少？Ifinformationhadbeensymmetric,bothownersandbuyerswereuncertainofthequality,theyonlyknowtheaveragequalityofcars,thenisthereamarketfortheusedcars?Whatwouldbethemarketprice?檸檬法則TheLemonsPrinciple如果信息對6檸檬法則的應(yīng)用：醫(yī)療保險ApplicationofTheLemonsPrinciple:HealthInsurance信息不對稱Informationasymmetry潛在的參保者比醫(yī)療保險公司更了解自己將來可能的醫(yī)療保健支出Thepotentialinsuredpersonknowsmoreabouther(his)expectedhealthexpendituresinthecomingperiodthandoestheinsurancecompany.具體地講Morespecifically參保者知道自己將來的醫(yī)療費用（類似于二手車的車主）Insuredknowsher(his)futureexpenditureexactly(similartotheownerofthecars)保險公司只了解所有參保者的醫(yī)療費用的分布（類似于買車的人）Insurancecompanyknowsonlythedistributionofexpendituresforallinsuredpersons(similartothebuyerofthecars)檸檬法則的應(yīng)用：醫(yī)療保險ApplicationofThe7檸檬法則的應(yīng)用：醫(yī)療保險ApplicationofTheLemonsPrinciple:HealthInsurance醫(yī)療保險市場有5個人Thereare5personsinhealthinsurancemarket預(yù)期的醫(yī)療費用＝0,?,?,?,1Expectedexpenditure=0,?,?,?,1平均醫(yī)療費用＝?Averageexpenditure=?我們再做一個游戲看醫(yī)療保險市場是否存在Wedothegameagaininclasstocheckifthereishealthinsurancemarket如果信息對稱，參保者和保險公司都只知道風(fēng)險的分布，那將會怎樣？Ifinformationhadbeensymmetric,bothinsuredandinsurancecompanyonlyknowthedistributionofexpenditure,then?檸檬法則的應(yīng)用：醫(yī)療保險ApplicationofThe8代理關(guān)系——委托代理問題AgencyRelationship—ThePrincipalAgentProblem代理關(guān)系A(chǔ)gencyrelationship委托方委托另一方，也就是代理方作出決定Aprincipaldelegatesdecision-makingauthoritytoanotherparty,theagent信息不對稱和代理問題是相關(guān)的現(xiàn)象Asymmetricinformationandagencyarecloselyrelatedphenomena委托代理問題ThePrincipalAgentProblem怎樣確定醫(yī)生作出了最符合患者利益的決策Howtodeterminethephysicianisactinginthepatient’sbestinterests代理關(guān)系——委托代理問題AgencyRelationshi9供給誘導(dǎo)需求Supplier-InducedDemand供給誘導(dǎo)需求問題TheSupplier-InducedDemandproblem醫(yī)生具有影響需求的利益驅(qū)動Thephysicianhasafinancialinteresttoinfluencethedemand.醫(yī)生可以通過提供不準(zhǔn)確的信息“創(chuàng)造”需求Thephysiciancan“create”thedemandbyprovidingthebiasedinformationtothepatient供給誘導(dǎo)需求問題源于信息不對稱TheSIDproblemresultsfromasymmetricinformation患者和保險方都缺乏作出關(guān)于醫(yī)療方面的決策的必要信息Bothpatientsandinsurerslackthenecessaryinformationtomakemanymedical-relateddecision患者依賴于醫(yī)生的建議和他們所提供的服務(wù)Thepatientdependsuponthephysicianforbothadviceandservice供給誘導(dǎo)需求Supplier-InducedDemand10供給誘導(dǎo)需求Supplier-InducedDemand傳統(tǒng)的經(jīng)濟(jì)學(xué)模型Thetraditionaleconomicmodel傳統(tǒng)的經(jīng)濟(jì)學(xué)模型假設(shè)醫(yī)生是患者完美的代理人，可以推出其他條件不變，供給的增加將降低醫(yī)生的收費，從而降低醫(yī)生的收入。Thetraditionaleconomicmodel,whichassumesthephysicianisaperfectagentforthepatient,wouldpredictthatanincreaseinsupply,otherthingsbeingequal,wouldresultinadeclineinphysician’sfees,andconsequentlyphysicianincomes.現(xiàn)實的觀察正好相反Theobservationinrealityisopposite需要更合理的理論解釋醫(yī)生的行為Needalternativetheorytostudyphysicianbehavior供給誘導(dǎo)需求Supplier-InducedDemand11S1S0D0E0E1供給誘導(dǎo)需求Supplier-InducedDemand傳統(tǒng)的經(jīng)濟(jì)學(xué)模型Thetraditionaleconomicmodel供給量增加價格下降MQ0Q1P0P1PmS1S0D0E0E1供給誘導(dǎo)需求Supplier-Indu12供給誘導(dǎo)需求Supplier-InducedDemand供給誘導(dǎo)需求的價格剛性模型ThepricerigiditymodelofSID為什么競爭的市場會出現(xiàn)誘導(dǎo)需求？一種解釋是假設(shè)醫(yī)療價格傾向于剛性O(shè)neapproachthatcanexplaindemandinducementwithinthecontextofacompetitivemarketmodelistoarguethatpricestendtoberigid隨著供給增加，為了保持固定的價格，醫(yī)生具有增加需求的激勵A(yù)ssupplyincreases,inordertofixtheprice,thephysicianhasincentivetoinducedemand但是這個理論只能解釋為何價格沒有下降，但不能解釋為何價格上升Butthismodelcanonlyexplainwhypricedoesn’tgodownandcan’texplainwhypricegoesup供給誘導(dǎo)需求Supplier-InducedDemand13D1供給誘導(dǎo)需求Supplier-InducedDemandSID的價格剛性模型ThepricerigiditymodelofSID供給量增加價格不變S1E0MQ0Q2P0PmS0D0E2D1供給誘導(dǎo)需求Supplier-InducedDema14供給誘導(dǎo)需求Supplier-InducedDemandSID的目標(biāo)收入模型ThetargetincomemodelofSID盡管醫(yī)生的供給快速增加，醫(yī)療價格仍然上升Thepriceofhealthcareincreasesdespiterapidincreaseinphysiciansupply目標(biāo)收入模型用以解釋醫(yī)生收費的快速上升Thetargetincomemodelisusedtoexplaintherapidincreaseinphysicianfees.在目標(biāo)收入假設(shè)下，醫(yī)生供給的增加導(dǎo)致收費的上升以保證目標(biāo)收入，或者醫(yī)生將誘導(dǎo)患者的需求以保證目標(biāo)收入Underthetargetincomehypothesis,increaseinsupplyofphysiciansleadtohigherfeesinorderforearningtobemaintained,orphysicianwillinducedemandtomaintainthetargetincome供給誘導(dǎo)需求Supplier-InducedDemand15供給誘導(dǎo)需求Supplier-InducedDemandSID的目標(biāo)收入模型ThetargetincomemodelofSID供給量增加價格上升D1S1E0S0D0E2MQ0Q2P0PmP1供給誘導(dǎo)需求Supplier-InducedDemand16供給誘導(dǎo)需求Supplier-InducedDemandSID的目標(biāo)收入模型ThetargetincomemodelofSID目標(biāo)收入假設(shè)的主要證據(jù)是醫(yī)生/人口比率和醫(yī)生收費呈正相關(guān)Themajorevidencefortargetincomehypothesisisthatphysician/populationratiosarepositivelyrelatedtophysicianfees醫(yī)生誘導(dǎo)需求的范圍和價格水平取決于醫(yī)生期望的收入目標(biāo)Theextentofthedemandthephysiciancancreateandthepricethatwillbeestablishedarebaseduponwhattargetincomethephysiciandesires目標(biāo)收入水平取決于當(dāng)?shù)氐氖杖胨?，尤其是其他醫(yī)生和專業(yè)人士的收入水平Thetargetincomeisdeterminedbythelocalincomedistribution,particularlywithrespecttotheincomeofotherphysiciansandprofessionals供給誘導(dǎo)需求Supplier-InducedDemand17供給誘導(dǎo)需求Supplier-InducedDemandSID的利潤最大化模型MQ1Q2P2PmP1MR2D1MC1MR1D2MC2供給誘導(dǎo)需求Supplier-InducedDemand18供給誘導(dǎo)需求Supplier-InducedDemandRoemer&Shain提出，一個地區(qū)增加床位的供給創(chuàng)造對床位的需求。為什么？供給誘導(dǎo)需求Supplier-InducedDemand19(1)短缺的存在如果制定的醫(yī)療價格低于均衡水平，即在P0處，S0表明床位供給，醫(yī)院利用為Q0。在P0價格上，就會出現(xiàn)Q3到Q0的過度需求。如果床位供給從S0增加到S1，從S1增加到S2，再至S3，醫(yī)院利用就會從Q0增加到Q3。供給誘導(dǎo)需求Supplier-InducedDemandS1S2S3S0Q0Q1Q2Q3DMP0Pm解釋一(1)短缺的存在供給誘導(dǎo)需求Supplier-Induc20(2)預(yù)計需求擴(kuò)大圖中S0&D0表示起始供求曲線，Q0為醫(yī)院服務(wù)利用。如果床位供給增加到S1，醫(yī)院服務(wù)利用增加到Q1，這種情況表明供給創(chuàng)造新的需求D1，相反，床位供給是建立在對需求增長的預(yù)測基礎(chǔ)上。供給誘導(dǎo)需求Supplier-InducedDemandD0S0D1S1MQ0Q1Pm(2)預(yù)計需求擴(kuò)大供給誘導(dǎo)需求Supplier-Indu21患者的往返成本發(fā)生了變化。如果增加的床位建在靠近預(yù)期患者的新型較小醫(yī)院，到醫(yī)院的往返成本將降低，這時，床位供給的增加并不創(chuàng)造新的需求，而是降低非貨幣成本(如路途的時間成本），使患者醫(yī)療總價格下降，從而使患者沿著其需求曲線向下移動。如圖：解釋二MQ1Q2P1P2Pm供給誘導(dǎo)需求Supplier-InducedDemand患者的往返成本發(fā)生了變化。如果增加的床位建在靠近預(yù)期患者的新22醫(yī)生通過收治患者入院來提高效益。解釋三供給誘導(dǎo)需求Supplier-InducedDemand還有其他解釋嗎？醫(yī)生通過收治患者入院來提高效益。解釋三供給誘導(dǎo)需求Supp23供給誘導(dǎo)需求Supplier-InducedDemand一項研究表明，平均每人受診數(shù)和一定人口擁有的醫(yī)生數(shù)量呈正相關(guān)，如一定人口擁有的外科醫(yī)生數(shù)每年增加10％，則手術(shù)例次增加3％。另一項研究表明，醫(yī)生按服務(wù)項目收費得到補(bǔ)償時，外科手術(shù)率是比較高的。某研究對有同樣保險賠付的雇員做了比較。其中一組按人頭預(yù)付計劃（capitation)，另一組按服務(wù)項目收費(fee-for-service)。結(jié)果發(fā)現(xiàn)住院手術(shù)處理率在按人頭付費為3.9,而在按項目收費中為7.0。在手術(shù)處理率的差別中，有1/3是闌尾切除術(shù)，扁桃體摘除術(shù)，女性外科手術(shù)（如剖腹產(chǎn)）等造成的。供給誘導(dǎo)需求Supplier-InducedDemand24供給誘導(dǎo)需求Supplier-InducedDemand供給誘導(dǎo)需求Supplier-InducedDemand25供給誘導(dǎo)需求Supplier-InducedDemand供給誘導(dǎo)需求Supplier-InducedDemand26供給誘導(dǎo)需求Supplier-InducedDemand供給誘導(dǎo)需求的識別問題TheidentificationproblemofSID實證研究中，誘導(dǎo)需求的影響無法用計量方法識別Intheempiricalwork,theSIDeffectcannotbeeconometricallyidentified很難區(qū)分患者的需求和醫(yī)生誘導(dǎo)的需求Itishardtodistinguishbetweenpatient’sdemandandphysician’sinduceddemand供給誘導(dǎo)需求Supplier-InducedDemand27供給誘導(dǎo)需求Supplier-InducedDemand供給誘導(dǎo)需求的成本ThecostsofSID時間成本Timecost聲譽下降Reputationloss“心理精神”成本“psychic”cost供給誘導(dǎo)需求Supplier-InducedDemand28供給誘導(dǎo)需求Supplier-InducedDemand避免醫(yī)生創(chuàng)造需求的方法：增加患者受教育水平可能會降低醫(yī)生創(chuàng)造額外需求的能力。當(dāng)患者被建議做手術(shù)時，應(yīng)從保險公司或其他醫(yī)生處獲得更多信息。向醫(yī)生提供經(jīng)濟(jì)刺激以避免不必要的手術(shù)。這些經(jīng)濟(jì)刺激主要包括，告訴醫(yī)生不必要的手術(shù)可能引起的醫(yī)療事故訴訟。供給誘導(dǎo)需求Supplier-InducedDemand29信息不對稱AsymmetricInformation信息問題InformationProblems患者——缺乏信息，也沒有能力識別質(zhì)量Patients—lackofinformationandinabilitytodiscernquality保險方——缺乏參保者的健康狀況信息Insurers—lackofinformationaboutindividual’shealthbackground逆向選擇Adverseselection假設(shè)有10個低風(fēng)險的人和10個高風(fēng)險的人，高風(fēng)險的人預(yù)期的醫(yī)療保健費是1000美元，低風(fēng)險的人預(yù)期的醫(yī)療保健費是100美元。醫(yī)療保險費的確定基于平均的預(yù)期醫(yī)療保健費，也就是550美元Supposethereare10lowriskpeopleand10highriskpeople,thehighriskpeople’sexpectedhealthcareexpenditurewillbe$1000,thelowrisk’swillbe$100.Thehealthinsurancepremiumisbasedonaverageexpectedexpenditure,whichis$550.

信息不對稱AsymmetricInformation信息30逆向選擇AdverseSelection保險公司無法區(qū)分風(fēng)險高和風(fēng)險低的人。保險費只反映了兩類人的平均風(fēng)險。因此高風(fēng)險的人將購買保險，因為此時的保險費低于完全依照他們的風(fēng)險確定的保險費。而低風(fēng)險的人可能不會購買保險，因為此時的保險費高于完全依照他們的風(fēng)險確定的保險費。Theinsurancecompanyisunabletodistinguishbetweenhighandlowrisks.Theinsurancepremiumonlyreflectstheaverageriskofthetwogroups.Then,thehighriskgroupwillpurchaseinsurancesinceapremiumbasedontheaverageriskislowerthanapremiumbasedsolelyontheirownrisk.Thelowriskindividualsmaynotpurchaseinsurancesinceapremiumbasedontheaveragewouldbegreaterthantheirownrisk-basedpremium.逆向選擇AdverseSelection保險公司無法區(qū)分31逆向選擇AdverseSelection逆向選擇將會導(dǎo)致某些人購買醫(yī)療保險Adverseselectionwouldresultinabiasedsampleofthosethatpurchasehealthinsurance更多的高風(fēng)險個人將購買保險Predominantly,morehighriskindividualswouldpurchaseinsurance“檸檬”法則TheLemonsPrinciple高風(fēng)險的人驅(qū)逐低風(fēng)險的人直至市場不存在Thebaddrivesoutthegooduntilnomarketisleft逆向選擇AdverseSelection逆向選擇將會導(dǎo)致32檸檬法則TheLemonsPrincipleAkerlof(1970)用信息不對稱的觀點分析二手車市場Akerlof(1970)usedtheideaofasymmetricinformationtoanalyzetheusedcarmarket二手車的質(zhì)量千差萬別Usedcarsavailableforsalevaryinquality對稱不信息Asymmetricinformation賣者比買者更了解車子的質(zhì)量Thesellersknowbetterthetruequalityoftheircarsthanthebuyers有9輛車供出售Thereare9carsforsale質(zhì)量(Q)=0,?,?,?,1,1?,1?,1?,2賣者了解每輛車的質(zhì)量Seller(owner)knowseachcar’squality買者只知道質(zhì)量的分布Buyeronlyknowsthedistributionofquality檸檬法則TheLemonsPrincipleAkerl33檸檬法則TheLemonsPrinciple賣者的保留價值是$1000xQ

Sellerhasareservevalue=$1000xQ買者的保留價值是$1,500xQ

Buyerhasareservevalue=$1,500xQ雇傭一個拍賣人報價。拍賣人找到一個需求量等于供給量的價格就成交Anauctioneerishiredtocalloutprices.Salestakeplacewhentheauctioneerfindsapricethatmakesquantitydemandedequalquantitysupplied我們現(xiàn)在進(jìn)行這個拍賣游戲Wedothesalesgametogetherinclass檸檬法則TheLemonsPrinciple賣者的保留34檸檬法則TheLemonsPrinciple如果信息對稱，買者和賣者都不清楚具體的質(zhì)量，他們只知道車子的平均質(zhì)量，此時二手車市場能否存在？市場價格是多少？Ifinformationhadbeensymmetric,bothownersandbuyerswereuncertainofthequality,theyonlyknowtheaveragequalityofcars,thenisthereamarketfortheusedcars?Whatwouldbethemarketprice?檸檬法則TheLemonsPrinciple如果信息對35檸檬法則的應(yīng)用：醫(yī)療保險ApplicationofTheLemonsPrinciple:HealthInsurance信息不對稱Informationasymmetry潛在的參保者比醫(yī)療保險公司更了解自己將來可能的醫(yī)療保健支出Thepotentialinsuredpersonknowsmoreabouther(his)expectedhealthexpendituresinthecomingperiodthandoestheinsurancecompany.具體地講Morespecifically參保者知道自己將來的醫(yī)療費用（類似于二手車的車主）Insuredknowsher(his)futureexpenditureexactly(similartotheownerofthecars)保險公司只了解所有參保者的醫(yī)療費用的分布（類似于買車的人）Insurancecompanyknowsonlythedistributionofexpendituresforallinsuredpersons(similartothebuyerofthecars)檸檬法則的應(yīng)用：醫(yī)療保險ApplicationofThe36檸檬法則的應(yīng)用：醫(yī)療保險ApplicationofTheLemonsPrinciple:HealthInsurance醫(yī)療保險市場有5個人Thereare5personsinhealthinsurancemarket預(yù)期的醫(yī)療費用＝0,?,?,?,1Expectedexpenditure=0,?,?,?,1平均醫(yī)療費用＝?Averageexpenditure=?我們再做一個游戲看醫(yī)療保險市場是否存在Wedothegameagaininclasstocheckifthereishealthinsurancemarket如果信息對稱，參保者和保險公司都只知道風(fēng)險的分布，那將會怎樣？Ifinformationhadbeensymmetric,bothinsuredandinsurancecompanyonlyknowthedistributionofexpenditure,then?檸檬法則的應(yīng)用：醫(yī)療保險ApplicationofThe37代理關(guān)系——委托代理問題AgencyRelationship—ThePrincipalAgentProblem代理關(guān)系A(chǔ)gencyrelationship委托方委托另一方，也就是代理方作出決定Aprincipaldelegatesdecision-makingauthoritytoanotherparty,theagent信息不對稱和代理問題是相關(guān)的現(xiàn)象Asymmetricinformationandagencyarecloselyrelatedphenomena委托代理問題ThePrincipalAgentProblem怎樣確定醫(yī)生作出了最符合患者利益的決策Howtodeterminethephysicianisactinginthepatient’sbestinterests代理關(guān)系——委托代理問題AgencyRelationshi38供給誘導(dǎo)需求Supplier-InducedDemand供給誘導(dǎo)需求問題TheSupplier-InducedDemandproblem醫(yī)生具有影響需求的利益驅(qū)動Thephysicianhasafinancialinteresttoinfluencethedemand.醫(yī)生可以通過提供不準(zhǔn)確的信息“創(chuàng)造”需求Thephysiciancan“create”thedemandbyprovidingthebiasedinformationtothepatient供給誘導(dǎo)需求問題源于信息不對稱TheSIDproblemresultsfromasymmetricinformation患者和保險方都缺乏作出關(guān)于醫(yī)療方面的決策的必要信息Bothpatientsandinsurerslackthenecessaryinformationtomakemanymedical-relateddecision患者依賴于醫(yī)生的建議和他們所提供的服務(wù)Thepatientdependsuponthephysicianforbothadviceandservice供給誘導(dǎo)需求Supplier-InducedDemand39供給誘導(dǎo)需求Supplier-InducedDemand傳統(tǒng)的經(jīng)濟(jì)學(xué)模型Thetraditionaleconomicmodel傳統(tǒng)的經(jīng)濟(jì)學(xué)模型假設(shè)醫(yī)生是患者完美的代理人，可以推出其他條件不變，供給的增加將降低醫(yī)生的收費，從而降低醫(yī)生的收入。Thetraditionaleconomicmodel,whichassumesthephysicianisaperfectagentforthepatient,wouldpredictthatanincreaseinsupply,otherthingsbeingequal,wouldresultinadeclineinphysician’sfees,andconsequentlyphysicianincomes.現(xiàn)實的觀察正好相反Theobservationinrealityisopposite需要更合理的理論解釋醫(yī)生的行為Needalternativetheorytostudyphysicianbehavior供給誘導(dǎo)需求Supplier-InducedDemand40S1S0D0E0E1供給誘導(dǎo)需求Supplier-InducedDemand傳統(tǒng)的經(jīng)濟(jì)學(xué)模型Thetraditionaleconomicmodel供給量增加價格下降MQ0Q1P0P1PmS1S0D0E0E1供給誘導(dǎo)需求Supplier-Indu41供給誘導(dǎo)需求Supplier-InducedDemand供給誘導(dǎo)需求的價格剛性模型ThepricerigiditymodelofSID為什么競爭的市場會出現(xiàn)誘導(dǎo)需求？一種解釋是假設(shè)醫(yī)療價格傾向于剛性O(shè)neapproachthatcanexplaindemandinducementwithinthecontextofacompetitivemarketmodelistoarguethatpricestendtoberigid隨著供給增加，為了保持固定的價格，醫(yī)生具有增加需求的激勵A(yù)ssupplyincreases,inordertofixtheprice,thephysicianhasincentivetoinducedemand但是這個理論只能解釋為何價格沒有下降，但不能解釋為何價格上升Butthismodelcanonlyexplainwhypricedoesn’tgodownandcan’texplainwhypricegoesup供給誘導(dǎo)需求Supplier-InducedDemand42D1供給誘導(dǎo)需求Supplier-InducedDemandSID的價格剛性模型ThepricerigiditymodelofSID供給量增加價格不變S1E0MQ0Q2P0PmS0D0E2D1供給誘導(dǎo)需求Supplier-InducedDema43供給誘導(dǎo)需求Supplier-InducedDemandSID的目標(biāo)收入模型ThetargetincomemodelofSID盡管醫(yī)生的供給快速增加，醫(yī)療價格仍然上升Thepriceofhealthcareincreasesdespiterapidincreaseinphysiciansupply目標(biāo)收入模型用以解釋醫(yī)生收費的快速上升Thetargetincomemodelisusedtoexplaintherapidincreaseinphysicianfees.在目標(biāo)收入假設(shè)下，醫(yī)生供給的增加導(dǎo)致收費的上升以保證目標(biāo)收入，或者醫(yī)生將誘導(dǎo)患者的需求以保證目標(biāo)收入Underthetargetincomehypothesis,increaseinsupplyofphysiciansleadtohigherfeesinorderforearningtobemaintained,orphysicianwillinducedemandtomaintainthetargetincome供給誘導(dǎo)需求Supplier-InducedDemand44供給誘導(dǎo)需求Supplier-InducedDemandSID的目標(biāo)收入模型ThetargetincomemodelofSID供給量增加價格上升D1S1E0S0D0E2MQ0Q2P0PmP1供給誘導(dǎo)需求Supplier-InducedDemand45供給誘導(dǎo)需求Supplier-InducedDemandSID的目標(biāo)收入模型ThetargetincomemodelofSID目標(biāo)收入假設(shè)的主要證據(jù)是醫(yī)生/人口比率和醫(yī)生收費呈正相關(guān)Themajorevidencefortargetincomehypothesisisthatphysician/populationratiosarepositivelyrelatedtophysicianfees醫(yī)生誘導(dǎo)需求的范圍和價格水平取決于醫(yī)生期望的收入目標(biāo)Theextentofthedemandthephysiciancancreateandthepricethatwillbeestablishedarebaseduponwhattargetincomethephysiciandesires目標(biāo)收入水平取決于當(dāng)?shù)氐氖杖胨?，尤其是其他醫(yī)生和專業(yè)人士的收入水平Thetargetincomeisdeterminedbythelocalincomedistribution,particularlywithrespecttotheincomeofother