信息不對(duì)稱(chēng) Asymmetric Ination(衛(wèi)生經(jīng)濟(jì)學(xué))

1、信息不對(duì)稱(chēng) asymmetric informationn信息問(wèn)題 information problemsn患者缺乏信息，也沒(méi)有能力識(shí)別質(zhì)量 patientslack of information and inability to discern qualityn保險(xiǎn)方缺乏參保者的健康狀況信息 insurerslack of information about individuals health backgroundn逆向選擇 adverse selectionn假設(shè)有10個(gè)低風(fēng)險(xiǎn)的人和10個(gè)高風(fēng)險(xiǎn)的人，高風(fēng)險(xiǎn)的人預(yù)期的醫(yī)療保健費(fèi)是1000美元，低風(fēng)險(xiǎn)的人預(yù)期的醫(yī)療保健費(fèi)是100美元。醫(yī)療

2、保險(xiǎn)費(fèi)的確定基于平均的預(yù)期醫(yī)療保健費(fèi)，也就是550美元suppose there are 10 low risk people and 10 high risk people, the high risk peoples expected health care expenditure will be $1000, the low risks will be $100. the health insurance premium is based on average expected expenditure, which is $550.逆向選擇 adverse selectionn保險(xiǎn)公司無(wú)

3、法區(qū)分風(fēng)險(xiǎn)高和風(fēng)險(xiǎn)低的人。 保險(xiǎn)費(fèi)只反映了兩類(lèi)人的平均風(fēng)險(xiǎn)。因此高風(fēng)險(xiǎn)的人將購(gòu)買(mǎi)保險(xiǎn)，因?yàn)榇藭r(shí)的保險(xiǎn)費(fèi)低于完全依照他們的風(fēng)險(xiǎn)確定的保險(xiǎn)費(fèi)。而低風(fēng)險(xiǎn)的人可能不會(huì)購(gòu)買(mǎi)保險(xiǎn)，因?yàn)榇藭r(shí)的保險(xiǎn)費(fèi)高于完全依照他們的風(fēng)險(xiǎn)確定的保險(xiǎn)費(fèi)。 the insurance company is unable to distinguish between high and low risks. the insurance premium only reflects the average risk of the two groups. then, the high risk group will purchase in

4、surance since a premium based on the average risk is lower than a premium based solely on their own risk. the low risk individuals may not purchase insurance since a premium based on the average would be greater than their own risk-based premium.逆向選擇 adverse selectionn逆向選擇將會(huì)導(dǎo)致某些人購(gòu)買(mǎi)醫(yī)療保險(xiǎn)adverse select

5、ion would result in a biased sample of those that purchase health insurancen更多的高風(fēng)險(xiǎn)個(gè)人將購(gòu)買(mǎi)保險(xiǎn) predominantly, more high risk individuals would purchase insurancen“檸檬”法則 the lemons principlen高風(fēng)險(xiǎn)的人驅(qū)逐低風(fēng)險(xiǎn)的人直至市場(chǎng)不存在 the bad drives out the good until no market is left檸檬法則 the lemons principlenakerlof (1970) 用信息

6、不對(duì)稱(chēng)的觀點(diǎn)分析二手車(chē)市場(chǎng) akerlof (1970) used the idea of asymmetric information to analyze the used car marketn二手車(chē)的質(zhì)量千差萬(wàn)別 used cars available for sale vary in qualityn對(duì)稱(chēng)不信息 asymmetric informationn賣(mài)者比買(mǎi)者更了解車(chē)子的質(zhì)量 the sellers know better the true quality of their cars than the buyersn有9輛車(chē)供出售 there are 9 cars for s

7、alen質(zhì)量(q)= 0, , , , 1, 1 , 1 , 1 , 2n賣(mài)者了解每輛車(chē)的質(zhì)量 seller(owner) knows each cars qualityn買(mǎi)者只知道質(zhì)量的分布 buyer only knows the distribution of quality 檸檬法則 the lemons principlen賣(mài)者的保留價(jià)值是$1000 xq seller has a reserve value=$1000 xqn買(mǎi)者的保留價(jià)值是$1,500 xq buyer has a reserve value=$1,500 xqn雇傭一個(gè)拍賣(mài)人報(bào)價(jià)。拍賣(mài)人找到一個(gè)需求量等于供給量

8、的價(jià)格就成交 an auctioneer is hired to call out prices. sales take place when the auctioneer finds a price that makes quantity demanded equal quantity suppliedn我們現(xiàn)在進(jìn)行這個(gè)拍賣(mài)游戲 we do the sales game together in class檸檬法則 the lemons principlen如果信息對(duì)稱(chēng)，買(mǎi)者和賣(mài)者都不清楚具體的質(zhì)量，他們只知道車(chē)子的平均質(zhì)量，此時(shí)二手車(chē)市場(chǎng)能否存在？市場(chǎng)價(jià)格是多少？ if informatio

9、n had been symmetric, both owners and buyers were uncertain of the quality, they only know the average quality of cars, then is there a market for the used cars? what would be the market price?檸檬法則的應(yīng)用：醫(yī)療保險(xiǎn)application of the lemons principle: health insurancen信息不對(duì)稱(chēng) information asymmetryn潛在的參保者比醫(yī)療保險(xiǎn)公司

10、更了解自己將來(lái)可能的醫(yī)療保健支出 the potential insured person knows more about her (his) expected health expenditures in the coming period than does the insurance company.n具體地講 more specificallyn參保者知道自己將來(lái)的醫(yī)療費(fèi)用（類(lèi)似于二手車(chē)的車(chē)主） insured knows her (his) future expenditure exactly (similar to the owner of the cars)n保險(xiǎn)公司只了解所有

11、參保者的醫(yī)療費(fèi)用的分布 （類(lèi)似于買(mǎi)車(chē)的人） insurance company knows only the distribution of expenditures for all insured persons(similar to the buyer of the cars) 檸檬法則的應(yīng)用：醫(yī)療保險(xiǎn)application of the lemons principle: health insurancen醫(yī)療保險(xiǎn)市場(chǎng)有5個(gè)人 there are 5 persons in health insurance marketn預(yù)期的醫(yī)療費(fèi)用0, , , , 1 expected expendi

12、ture=0, , , , 1n平均醫(yī)療費(fèi)用 average expenditure= n我們?cè)僮鲆粋€(gè)游戲看醫(yī)療保險(xiǎn)市場(chǎng)是否存在 we do the game again in class to check if there is health insurance marketn如果信息對(duì)稱(chēng)，參保者和保險(xiǎn)公司都只知道風(fēng)險(xiǎn)的分布，那將會(huì)怎樣？ if information had been symmetric, both insured and insurance company only know the distribution of expenditure, then?代理關(guān)系委托代理問(wèn)題

13、agency relationshipthe principal agent problemn代理關(guān)系 agency relationshipn委托方委托另一方，也就是代理方作出決定 a principal delegates decision-making authority to another party, the agentn信息不對(duì)稱(chēng)和代理問(wèn)題是相關(guān)的現(xiàn)象 asymmetric information and agency are closely related phenomenan委托代理問(wèn)題 the principal agent problemn怎樣確定醫(yī)生作出了最符合患者利益

14、的決策 how to determine the physician is acting in the patients best interests供給誘導(dǎo)需求 supplier-induced demandn供給誘導(dǎo)需求問(wèn)題 the supplier-induced demand problemn醫(yī)生具有影響需求的利益驅(qū)動(dòng) the physician has a financial interest to influence the demand. n醫(yī)生可以通過(guò)提供不準(zhǔn)確的信息“創(chuàng)造”需求 the physician can “create” the demand by providin

15、g the biased information to the patientn供給誘導(dǎo)需求問(wèn)題源于信息不對(duì)稱(chēng) the sid problem results from asymmetric informationn患者和保險(xiǎn)方都缺乏作出關(guān)于醫(yī)療方面的決策的必要信息 both patients and insurers lack the necessary information to make many medical-related decisionn患者依賴于醫(yī)生的建議和他們所提供的服務(wù) the patient depends upon the physician for both ad

16、vice and service供給誘導(dǎo)需求 supplier-induced demandn傳統(tǒng)的經(jīng)濟(jì)學(xué)模型 the traditional economic modeln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(fèi)，從而降低醫(yī)生的收入。 the traditional economic model, which assumes the physician is a perfect agent for the patient, would predict that an increase in supply, other things bein

17、g equal, would result in a decline in physicians fees, and consequently physician incomes.n現(xiàn)實(shí)的觀察正好相反 the observation in reality is oppositen需要更合理的理論解釋醫(yī)生的行為 need alternative theory to study physician behaviors1s0d0e0e1供給誘導(dǎo)需求 supplier-induced demandn傳統(tǒng)的經(jīng)濟(jì)學(xué)模型 the traditional economic modeln供給量增加n價(jià)格下降mq

18、0q1p0p1pm供給誘導(dǎo)需求 supplier-induced demandn供給誘導(dǎo)需求的價(jià)格剛性模型 the price rigidity model of sidn為什么競(jìng)爭(zhēng)的市場(chǎng)會(huì)出現(xiàn)誘導(dǎo)需求？一種解釋是假設(shè)醫(yī)療價(jià)格傾向于剛性 one approach that can explain demand inducement within the context of a competitive market model is to argue that prices tend to be rigidn隨著供給增加，為了保持固定的價(jià)格，醫(yī)生具有增加需求的激勵(lì) as supply incr

19、eases, in order to fix the price, the physician has incentive to induce demandn但是這個(gè)理論只能解釋為何價(jià)格沒(méi)有下降，但不能解釋為何價(jià)格上升 but this model can only explain why price doesnt go down and cant explain why price goes upd1供給誘導(dǎo)需求 supplier-induced demandnsid的價(jià)格剛性模型 the price rigidity model of sidn供給量增加n價(jià)格不變s1e0mq0q2p0pm

20、s0d0e2供給誘導(dǎo)需求 supplier-induced demandnsid的目標(biāo)收入模型 the target income model of sidn盡管醫(yī)生的供給快速增加，醫(yī)療價(jià)格仍然上升 the price of health care increases despite rapid increase in physician supplyn目標(biāo)收入模型用以解釋醫(yī)生收費(fèi)的快速上升 the target income model is used to explain the rapid increase in physician fees. n在目標(biāo)收入假設(shè)下，醫(yī)生供給的增加導(dǎo)致收費(fèi)

21、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 under the target income hypothesis, increase in supply of physicians lead to higher fees in order for earning to be maintained, or physician will induce demand to maintain the target income供給誘導(dǎo)需求 supplier-induced demandnsid的目標(biāo)收入模型 the target income model of sidn供給量增加n價(jià)

22、格上升d1s1e0s0d0e2mq0q2p0pmp1供給誘導(dǎo)需求 supplier-induced demandnsid的目標(biāo)收入模型 the target income model of sidn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(fèi)呈正相關(guān) the major evidence for target income hypothesis is that physician/population ratios are positively related to physician feesn醫(yī)生誘導(dǎo)需求的范圍和價(jià)格水平取決于醫(yī)生期望的收入目標(biāo) the extent of the de

23、mand the physician can create and the price that will be established are based upon what target income the physician desiresn目標(biāo)收入水平取決于當(dāng)?shù)氐氖杖胨剑绕涫瞧渌t(yī)生和專(zhuān)業(yè)人士的收入水平 the target income is determined by the local income distribution, particularly with respect to the income of other physicians and profession

24、als供給誘導(dǎo)需求 supplier-induced demandnsid的利潤(rùn)最大化模型mq1q2p2pmp1mr2d1mc1mr1d2mc2供給誘導(dǎo)需求 supplier-induced demandnroemer & shain 提出，一個(gè)地區(qū)增加床位的供給創(chuàng)造對(duì)床位的需求。為什么？(1) 短缺的存在如果制定的醫(yī)療價(jià)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(jià)格上，就會(huì)出現(xiàn)q3到q0的過(guò)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(huì)從q0增加到q3。供給誘導(dǎo)需求 supplier-induced demands1s2s3

25、s0q0q1q2q3dmp0pm解釋一解釋一(2) 預(yù)計(jì)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(duì)需求增長(zhǎng)的預(yù)測(cè)基礎(chǔ)上。供給誘導(dǎo)需求 supplier-induced demandd0s0d1s1mq0q1pm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(shí)，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(shí)間成本），使患者醫(yī)療總價(jià)格下降，從而使患者沿著其需求曲線向下移動(dòng)。如圖：解釋二解釋二mq1q2p1p2pm供給誘導(dǎo)需求 supplier-induced demand醫(yī)生通過(guò)收治患者入院來(lái)提高效益。解釋三解釋三供給誘導(dǎo)需求 supplier-induced demand還有其他解釋嗎？供給誘導(dǎo)需求 supplier-induced demandn一項(xiàng)研究表