Transcript 风险厌恶程度

医疗保健市场
医疗消费的上涨
Figure 9.1: US expenditures of selected goods and services as share of Gross Domestic Product (19602004)
18
16
Percentage of GDP
14
12
10
8
6
4
2
0
1960
1964
1968
1972
1976
1980
1984
1988
1992
1996
2000
Year
Health
Food
Clothing and Shoes
Housing
SOURCE: US Census Bureau [2006, pp. 98, 443], and National Income and Product Accounts
(http://www.bea.gov/bea/dn/nipaweb/index.asp.
2004
社会保险Social Insurance
• 政府提供的抵御风险的手段（养老、医疗、失业、工
伤、生育）
• 美国的社会保险
• Medicaid
• Medicare
• Social Security
• Unemployment Compensation
医疗保险的运行原理
• 风险规避倾向
• 保险费的决定
• Expected Value
• Expected value (EV) = probability of outcome 1) *
(Payout in outcome 1) + probability of outcome
2)*(Payout in outcome 2) + … + (probability of
outcome n)*(Payout in outcome n)
对医疗保险的需求
健康时，收入＝Y,
效用=U(H)
生病时, 收入＝ Y-C,
效用=U(S)
期望效用=E(U).
AB之间的距离表示风险
规避的程度
期望效用E(U)等于确定性情况下收入为Y2
时的效用
个体愿意支付的保险费最多为Y-Y2
为什么要购买保险？
(A)
(B)
(C)
Income
if She
Stays
Healthy
Income if
She Gets
Sick
Expecte
d Value
Insurance
Options
Income
Probability
of Staying
Healthy
Probability
of Getting
Sick
Lost
Income if
She Gets
Sick
Option 1: No
Insurance
$50,00
0
9 in 10
1 in 10
$30,000
$50,000
$20,000
$47,000
Option 2: Full
Insurance
($3,000
premium to
cover $30,000
in losses
$50,00
0
9 in 10
1 in 10
$30,000
$47,000
$47,000
$47,000
Actuarially Fair Insurance Policy
Utility
为什么要购买保险？
B
UB
UD
UC
D
C
• Expected
Utility
A
• Risk
Smoothing
UA
20,000
47,000 50,000
Income
为什么人们愿意支付附加保费?
• Risk Aversion
• Risk Premium
• Loading Fee
相关概念
• Risk Aversion：风险厌恶程度，效用函数的形状弯曲程度
越大（收入的边际效用递减速度越快），风险厌恶程度越
高
• Risk Premium：风险溢价，由于风险厌恶程度较高，而愿
意支付的较高的保险费
• Loading Fee：实际保险费高于精算平衡保费的部分（保险
公司的运行成本和利润）
风险分担的作用
•
•
•
•
Insurance in a small population
Insurance in a large population
Law of large numbers大数定律
参加人数越多，其风险越可以预测
医疗保险市场中的逆选择（adverse
selection)
• 信息不对称问题
• 投保人比保险公司拥有更多信息
• 保险公司按照平均风险概率和支出制定保险费，由此，
高风险和低风险的投保人面临相同保险费，低风险的
人会退出市场
• 有效率的做法应该是对高风险的人收高保费，对低风
险的人收低保费
信息不对称与逆选择
(A)
Probability of
Insurance
Buyer
Getting Sick
(B)
(C)
按风
险程
度收
费
统一
收取
较低
保费
统一
收取
较高
保费
(D)
(E)
(F)
Expected
Benefit
Expected
Benefit
Expected
Benefit
Minus
Premium
Minus
Premium
(Premium =
$3,000)
(Premium =
$4,500)
Lost
Income
Expected
Minus
Premium
if Sick
Lost
Income
(Differential
Premiums)
Emily
1 in 5 (High Risk)
$30,000
$6,000
$0
$3,000
$1,500
Jacob
1 in 5 (High Risk)
$30,000
$6,000
$0
$3,000
$1,500
Emma
1 in 5 (High Risk)
$30,000
$6,000
$0
$3,000
$1,500
Michael
1 in 5 (High Risk)
$30,000
$6,000
$0
$3,000
$1,500
Madison
1 in 5 (High Risk)
$30,000
$6,000
$0
$3,000
$1,500
Joshua
1 in 10 (Low Risk)
$30,000
$3,000
$0
$0
-$1,500
Olivia
1 in 10 (Low Risk)
$30,000
$3,000
$0
$0
-$1,500
Matthew
1 in 10 (Low Risk)
$30,000
$3,000
$0
$0
-$1,500
Hannah
1 in 10 (Low Risk)
$30,000
$3,000
$0
$0
-$1,500
Ethan
1 in 10 (Low Risk)
$30,000
$3,000
$0
$0
-$1,500
$0
-$15,000
$0
Insurer's
Net Profits
政府干预医疗保险的理由
• 逆选择是否是政府干预市场的理由？市场是否有能力
减轻逆选择？
• Experience rating：保险公司搜集信息，筛选客户，提
高效率，但产生公平问题
• Experience rating and equity：政府的强制性保险政策，
在效率和公平之间寻找平衡
• Community rating：团体费率
医疗保险市场的道德风险
•
•
•
•
道德风险：
扣除额（Deductible）
共同支付（Co-payment）
共同保险（Co-insurance）
Price per unit
道德风险
Flat-of-the-curve medicine
deadweight loss
P0
a
b
h
.2P0
0
Sm
Dm
M0
M1
Medical services per year
医疗支出与结果比较
医疗服务的需求弹性
• The Elasticity of Demand for Medical Services道德风险
的程度与需求弹性有关
• Social experiments find that the elasticity of demand for
health care is -0.20.
• 道德风险还与共保率有关
政府干预能消除道德风险吗？
• 道德风险引起的效率问题不是私人市场独有的，只要
存在第三方（医疗保险）支付费用，就会出现道德风
险
• 政府并不比市场能更好地控制道德风险
• 医疗保险的作用：在分担风险和道德风险之间寻找平
衡
引起医疗市场失灵的其他因素
• 信息问题：人们对疾病的知识有限；确定医疗质量的
困难
• 外部性：如传染病预防
• 上述两方面的问题是政府干预的理由之一
医疗费用的上涨
Health Expenditures as Percentage of GDP
Figure 9.5: Expenditures on health care as share of Gross Domestic Product, selected countries
(1960-2004)
16
14
12
10
8
6
4
2
0
1960
1970
1980
1990
2000
2004
Year
Australia
Canada
France
Germany
Japan
United Kingdom
United States
医疗费用上涨的原因
• 可能的原因
• The “graying” of America – older populations require
more health care
• Income growth – health care is a normal good
• Third party payments – insurance coverage may have
changed
• Improvements in quality – treatments are very
different (better and more expensive) than in previous
decade