信息不對稱AsymmetricInation(衛(wèi)生經(jīng)濟(jì)學(xué)).ppt

1、信息不對稱 Asymmetric Information,信息問題 Information Problems 患者缺乏信息，也沒有能力識別質(zhì)量 Patientslack of information and inability to discern quality 保險方缺乏參保者的健康狀況信息 Insurerslack of information about individuals health background 逆向選擇 Adverse selection 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

2、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 Selection,保險公司

3、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。 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 i

4、nsurance 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 Selection,逆向選擇將會導(dǎo)致某些人購買醫(yī)療保險Adverse sele

5、ction would result in a biased sample of those that purchase health insurance 更多的高風(fēng)險個人將購買保險 Predominantly, more high risk individuals would purchase insurance “檸檬”法則 The Lemons Principle 高風(fēng)險的人驅(qū)逐低風(fēng)險的人直至市場不存在 The bad drives out the good until no market is left,檸檬法則 The Lemons Principle,Akerlof (1970)

6、用信息不對稱的觀點分析二手車市場 Akerlof (1970) used the idea of asymmetric information to analyze the used car market 二手車的質(zhì)量千差萬別 Used cars available for sale vary in quality 對稱不信息 Asymmetric information 賣者比買者更了解車子的質(zhì)量 The sellers know better the true quality of their cars than the buyers 有9輛車供出售 There are 9 cars fo

7、r sale 質(zhì)量(Q)= 0, , , , 1, 1 , 1 , 1 , 2 賣者了解每輛車的質(zhì)量 Seller(owner) knows each cars quality 買者只知道質(zhì)量的分布 Buyer only knows the distribution of quality,檸檬法則 The Lemons Principle,賣者的保留價值是$1000 xQ Seller has a reserve value=$1000 xQ 買者的保留價值是$1,500 xQ Buyer has a reserve value=$1,500 xQ 雇傭一個拍賣人報價。拍賣人找到一個需求量等于

8、供給量的價格就成交 An auctioneer is hired to call out prices. Sales take place when the auctioneer finds a price that makes quantity demanded equal quantity supplied 我們現(xiàn)在進(jìn)行這個拍賣游戲 We do the sales game together in class,檸檬法則 The Lemons Principle,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？ If inform

9、ation 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Application of The Lemons Principle: Health Insurance,信息不對稱 Information asymmetry 潛在的參保者比醫(yī)

10、療保險公司更了解自己將來可能的醫(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. 具體地講 More specifically 參保者知道自己將來的醫(yī)療費用（類似于二手車的車主） Insured knows her (his) future expenditure exactly (similar to the owner of the cars) 保險公司

11、只了解所有參保者的醫(yī)療費用的分布 （類似于買車的人） 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Application of The Lemons Principle: Health Insurance,醫(yī)療保險市場有5個人 There are 5 persons in health insurance market 預(yù)期的醫(yī)療費用0, , , , 1 Expected ex

12、penditure=0, , , , 1 平均醫(yī)療費用 Average expenditure= 我們再做一個游戲看醫(yī)療保險市場是否存在 We do the game again in class to check if there is health insurance market 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？ If information had been symmetric, both insured and insurance company only know the distribution of expenditure, then?,代理關(guān)系委

13、托代理問題Agency RelationshipThe Principal Agent Problem,代理關(guān)系 Agency relationship 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 agent 信息不對稱和代理問題是相關(guān)的現(xiàn)象 Asymmetric information and agency are closely related phenomena 委托代理問題 The Principal Agent Problem 怎樣確定醫(yī)生作出了最符

14、合患者利益的決策 How to determine the physician is acting in the patients best interests,供給誘導(dǎo)需求 Supplier-Induced Demand,供給誘導(dǎo)需求問題 The Supplier-Induced Demand problem 醫(yī)生具有影響需求的利益驅(qū)動 The physician has a financial interest to influence the demand. 醫(yī)生可以通過提供不準(zhǔn)確的信息“創(chuàng)造”需求 The physician can “create” the demand by pro

15、viding the biased information to the patient 供給誘導(dǎo)需求問題源于信息不對稱 The SID problem results from asymmetric information 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 Both patients and insurers lack the necessary information to make many medical-related decision 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 bo

16、th advice and service,供給誘導(dǎo)需求 Supplier-Induced Demand,傳統(tǒng)的經(jīng)濟(jì)學(xué)模型 The traditional economic model 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。 The traditional economic model, which assumes the physician is a perfect agent for the patient, would predict that an increase in supply, other thing

17、s being equal, would result in a decline in physicians fees, and consequently physician incomes. 現(xiàn)實的觀察正好相反 The observation in reality is opposite 需要更合理的理論解釋醫(yī)生的行為 Need alternative theory to study physician behavior,供給誘導(dǎo)需求 Supplier-Induced Demand,傳統(tǒng)的經(jīng)濟(jì)學(xué)模型 The traditional economic model 供給量增加 價格下降,供給誘導(dǎo)

18、需求 Supplier-Induced Demand,供給誘導(dǎo)需求的價格剛性模型 The price rigidity model of SID 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 One approach that can explain demand inducement within the context of a competitive market model is to argue that prices tend to be rigid 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 As supply increases, in ord

19、er to fix the price, the physician has incentive to induce demand 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 But this model can only explain why price doesnt go down and cant explain why price goes up,供給誘導(dǎo)需求 Supplier-Induced Demand,SID的價格剛性模型 The price rigidity model of SID 供給量增加 價格不變,供給誘導(dǎo)需求 Supplier-Induced De

20、mand,SID的目標(biāo)收入模型 The target income model of SID 盡管醫(yī)生的供給快速增加，醫(yī)療價格仍然上升 The price of health care increases despite rapid increase in physician supply 目標(biāo)收入模型用以解釋醫(yī)生收費的快速上升 The target income model is used to explain the rapid increase in physician fees. 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 Un

21、der 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 Demand,SID的目標(biāo)收入模型 The target income model of SID 供給量增加 價格上升,供給誘導(dǎo)需求 Supplier-Induced Dema

22、nd,SID的目標(biāo)收入模型 The target income model of SID 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) The major evidence for target income hypothesis is that physician/population ratios are positively related to physician fees 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) The extent of the demand the physician can create and the price that will

23、be established are based upon what target income the physician desires 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 The target income is determined by the local income distribution, particularly with respect to the income of other physicians and professionals,供給誘導(dǎo)需求 Supplier-Induced Demand,SID的利潤最大化模型,供給誘導(dǎo)需求

24、Supplier-Induced Demand,Roemer & 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？,(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-Induced Demand,解釋一,(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，

25、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-Induced Demand,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,供給誘導(dǎo)需求 Supplier-Induced Demand,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-Induced Demand,還有其他解釋嗎？,供給誘導(dǎo)需求 Supplier-Induced Demand,一項研究表明，平均每人受診數(shù)和一定人口擁有的醫(yī)