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1、信息不对称 Asymmetric Information,信息问题 Information Problems 患者缺乏信息，也没有能力识别质量 Patientslack of information and inability to discern quality 保险方缺乏参保者的健康状况信息 Insurerslack of information about individuals health background 逆向选择 Adverse selection 假设有10个低风险的人和10个高风险的人，高风险的人预期的医疗保健费是1000美元，低风险的人预期的医疗保健费是100美元。医疗
2、保险费的确定基于平均的预期医疗保健费，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.,逆向选择 Adverse Selection,保险公司
3、无法区分风险高和风险低的人。 保险费只反映了两类人的平均风险。因此高风险的人将购买保险，因为此时的保险费低于完全依照他们的风险确定的保险费。而低风险的人可能不会购买保险，因为此时的保险费高于完全依照他们的风险确定的保险费。 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.,逆向选择 Adverse Selection,逆向选择将会导致某些人购买医疗保险Adverse sele
5、ction would result in a biased sample of those that purchase health insurance 更多的高风险个人将购买保险 Predominantly, more high risk individuals would purchase insurance “柠檬”法则 The Lemons Principle 高风险的人驱逐低风险的人直至市场不存在 The bad drives out the good until no market is left,柠檬法则 The Lemons Principle,Akerlof (1970)
6、用信息不对称的观点分析二手车市场 Akerlof (1970) used the idea of asymmetric information to analyze the used car market 二手车的质量千差万别 Used cars available for sale vary in quality 对称不信息 Asymmetric information 卖者比买者更了解车子的质量 The sellers know better the true quality of their cars than the buyers 有9辆车供出售 There are 9 cars fo
7、r sale 质量(Q)= 0, , , , 1, 1 , 1 , 1 , 2 卖者了解每辆车的质量 Seller(owner) knows each cars quality 买者只知道质量的分布 Buyer only knows the distribution of quality,柠檬法则 The Lemons Principle,卖者的保留价值是$1000xQ Seller has a reserve value=$1000xQ 买者的保留价值是$1,500xQ Buyer has a reserve value=$1,500xQ 雇佣一个拍卖人报价。拍卖人找到一个需求量等于供给量的
8、价格就成交 An auctioneer is hired to call out prices. Sales take place when the auctioneer finds a price that makes quantity demanded equal quantity supplied 我们现在进行这个拍卖游戏 We do the sales game together in class,柠檬法则 The Lemons Principle,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？ 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?,柠檬法则的应用：医疗保险Application of The Lemons Principle: Health Insurance,信息不对称 Information asymmetry 潜在的参保者比医疗保险公
10、司更了解自己将来可能的医疗保健支出 The potential insured person knows more about her (his) expected health expenditures in the coming period than does the insurance company. 具体地讲 More specifically 参保者知道自己将来的医疗费用（类似于二手车的车主） Insured knows her (his) future expenditure exactly (similar to the owner of the cars) 保险公司只了解所
11、有参保者的医疗费用的分布 （类似于买车的人） Insurance company knows only the distribution of expenditures for all insured persons(similar to the buyer of the cars),柠檬法则的应用：医疗保险Application of The Lemons Principle: Health Insurance,医疗保险市场有5个人 There are 5 persons in health insurance market 预期的医疗费用0, , , , 1 Expected expend
12、iture=0, , , , 1 平均医疗费用 Average expenditure= 我们再做一个游戏看医疗保险市场是否存在 We do the game again in class to check if there is health insurance market 如果信息对称，参保者和保险公司都只知道风险的分布，那将会怎样？ If information had been symmetric, both insured and insurance company only know the distribution of expenditure, then?,代理关系委托代理问
13、题Agency RelationshipThe Principal Agent Problem,代理关系 Agency relationship 委托方委托另一方，也就是代理方作出决定 A principal delegates decision-making authority to another party, the agent 信息不对称和代理问题是相关的现象 Asymmetric information and agency are closely related phenomena 委托代理问题 The Principal Agent Problem 怎样确定医生作出了最符合患者利
14、益的决策 How to determine the physician is acting in the patients best interests,供给诱导需求 Supplier-Induced Demand,供给诱导需求问题 The Supplier-Induced Demand problem 医生具有影响需求的利益驱动 The physician has a financial interest to influence the demand. 医生可以通过提供不准确的信息“创造”需求 The physician can “create” the demand by providing the biased information to the patient 供给诱导需求问题源于信息不对称 The SID problem results from asymmetric information 患者和保险方都缺乏作出关于医疗方面的决策的必要信息 Both patients and insur
