医疗保险 Health Insurance,医疗保险 Health Insurance 提供一种分散由疾病引起的财务风险的方式 Provide a way to diversify financial risks associated with illness 医疗保险的需求理论 The theory of demand for health insurance 个人希望最大化其效用 An individual wishes to maximize his or her utility 如果事件确定，每个人最大化其确定的效用 if there are certain events, individual maximizes his or her certainty utility 如果事件不确定，每个人最大化其期望效用 if there are uncertain events, individual maximizes his or her expected utility,医疗保险 Health Insurance,期望效用 Expected utility 生病的概率生病时的财富所带来的效用健康的概率健康时的财富所带来的效用 =probability of illness utility of wealth with illness + probability of healthy utility of wealth with healthy 例子，假设 Example, assume 约翰有$20,000 的年收入，年内没有储蓄和贷款 John has $20,000 annual income, no saving and borrowing 健康的概率95% ，医疗支出为0，财富为$20,000 With 95% probability, he will be healthy. When he is healthy, his health care expenditure is 0 and his wealth is $20,000 生病的概率5% ，医疗支出$10,000 ，财富$10,000 with 5% probability, he will be sick. When he is sick, his health care expenditure is $10,000 and his wealth is reduced to $10,000.,医疗保险 Health Insurance,两种可选的行动方案 Two alternative courses of action 他可以购买保险，承担一个数目不大的保险费 He can purchase insurance and incur a small loss in the form of the insurance premium 他也可以自我保险 He can self-insure 生病概率小，但是一旦生病损失很大 small possibility of a large loss if the illness occurs 不生病的概率大，也没有医疗支出 large possibility that the medical loss will not occur 问题：哪种选择可以使他的效用最大化？ Question: which choice provides him with a higher level of utility,医疗保险 Health Insurance,如果约翰购买医疗保险 If John would buy health insurance 保险费预期医疗保健支出 insurance premium= expected health care expenditure =95% 0 + 5%10,000 =500 他的财富 20,000-500=19500 His wealth =20,000-500=19500 他的确定效用 His certainty utility= 如果约翰不愿购买医保 If John wouldnt buy health insurance 他的财富将是$20,000 或者$10,000 his wealth could be $20,000 or $10,000 他的预期效用 his expected utility=,医疗保险 Health Insurance,约翰的偏好财富的效用 Johns preference-utility of wealth 财富 效用 边际效用 10,000 100 12,000 130 14,000 155 16,000 168 18,000 176 19,500 178 20,000 180,医疗保险 Health Insurance,约翰的财富的效用 Johns utility of wealth 如果他购买保险，其确定效用 if he would buy insurance, his certainty utility= U(财富=19500)=178 如果他不愿购买保险，其期望效用 if he wouldnt buy insurance,his expected utility= 5% U(w=10,000) + 95% U(w=20,000) =5% 100 + 95% 180 = 176 约翰的确定效用大于期望效用 Johns certainty utility is greater than the expected utility 如果购买保险，情况将得到改善 He will be better off if he buys insurance 不确定性导致效用损失 uncertainty leads to a loss of utility,医疗保险 Health Insurance,效用函数对购买保险行为的影响 The role of utility function in the purchase of insurance 线性效用函数，边际效用不变 Utility is linear function of wealth and marginal utility is constant 财富 效用 边际效用 10,000 100 12,000 120 14,000 140 16,000 160 18,000 180 19,500 195 20,000 200,医疗保险 Health Insurance,效用函数 Utility function U = a Y, Y=财富 U=0.01Y 利用约翰的例子 use Johns example 他的确定效用= 他的期望效用= 确定效用期望效用 His certainty utility = his expected utility 他是风险中性的 he is risk neutral,医疗保险 Health Insurance,医疗保险 Health Insurance,效用函数对购买保险行为的影响 The role of utility function in the purchase of insurance 效用函数是财富的增函数，边际效用递增 Utility is increasing function of wealth and marginal utility is increasing 财富 效用 边际效用 10,000 100 12,000 130 14,000 165 16,000 205 18,000 250 19,500 280 20,000 300,医疗保险 Health Insurance,效用函数 Utility function U = a Yb, Y=财富, b 1 U=0.01Yb 利用约翰的例子 use Johns example 他的确定效用= 他的期望效用= 确定效用期望效用 His certainty utility his expected utility 他是风险偏好者 he is risk lover 他不愿购买保险 he will not buy insurance,医疗保险 Health Insurance,医疗保险 Health Insurance,效用函数对购买保险行为的影响 The role of utility function in the purchase of insurance 效用函数是财富的增函数，边际效用递减 Utility is increasing function of wealth and marginal utility is increasing U=a Yb, b期望效用 His certainty utilityhis expected utility 他将购买保险 he will buy insurance 他是风险规避者 he is risk averse,医疗保险 Health Insurance,医疗保险 Health Insurance,纯保险金 Pure premium 预期医疗支出 expected health expenditure 额外费用 Loading cost 执行保险政策时所发生的管理费用和其他相关费用administrative and other costs associated with underwriting an insurance poli