Nicholson Sean, Bundorf Kate, Stein Rebecca M, Polsky Daniel
Cornell University, Ithaca, NY 14853, USA.
Health Serv Res. 2004 Dec;39(6 Pt 1):1817-38. doi: 10.1111/j.1475-6773.2004.00320.x.
To determine whether health maintenance organizations (HMOs) attract enrollees who use relatively few medical resources and whether a simple risk-adjustment system could mitigate or eliminate the inefficiency associated with risk selection.
The first and second rounds of the Community Tracking Study Household Survey (CTSHS), a national panel data set of households in 60 different markets in the United States.
We use regression analysis to examine medical expenditures in the first round of the survey between enrollees who switched plan types (i.e., from a non-HMO plan to an HMO plan, or vice versa) between the first and second rounds of the survey versus enrollees who remained in their original plan. The dependent variable is an enrollee's medical resource use, measured in dollars, and the independent variables include gender, age, self-reported health status, and other demographic variables.
We restrict our analysis to the 6,235 non-elderly persons who were surveyed in both rounds of the CTSHS, received health insurance from their employer or the employer of a household member in both years of the survey, and were offered a choice of an HMO and a non-HMO plan in both years.
We find that people who switched from a non-HMO to an HMO plan used 11 percent fewer medical services in the period prior to switching than people who remained in a non-HMO plan, and that this relatively low use persisted once they enrolled in an HMO. Furthermore, people who switched from an HMO to a non-HMO plan used 18 percent more medical services in the period prior to switching than those who remained in an HMO plan.
HMOs are experiencing favorable risk selection and would most likely continue to do so even if employers adjusted health plan payments based on enrollees' gender and age because the selection is based on enrollee characteristics that are difficult to observe, such as preferences for medical care and health status.
确定健康维护组织（HMO）是否吸引使用相对较少医疗资源的参保人，以及一个简单的风险调整系统能否减轻或消除与风险选择相关的低效率。
社区追踪研究家庭调查（CTSHS）的第一轮和第二轮调查，这是一个关于美国60个不同市场家庭的全国性面板数据集。
我们使用回归分析来研究在第一轮调查到第二轮调查期间，更换计划类型（即从非HMO计划转换为HMO计划，或反之）的参保人与保持原计划的参保人之间的医疗支出情况。因变量是参保人的医疗资源使用情况，以美元衡量，自变量包括性别、年龄、自我报告的健康状况以及其他人口统计学变量。
我们将分析限制在6235名非老年人身上，他们在CTSHS的两轮调查中均接受了调查，在调查的两年中均从其雇主或家庭成员的雇主处获得医疗保险，并且在这两年中都有HMO计划和非HMO计划可供选择。
我们发现，从非HMO计划转换为HMO计划的人在转换前的时期内使用的医疗服务比留在非HMO计划中的人少11%，并且在他们加入HMO后，这种相对较低的使用量仍然持续。此外，从HMO计划转换为非HMO计划的人在转换前的时期内使用的医疗服务比留在HMO计划中的人多18%。
HMO正在经历有利的风险选择，并且即使雇主根据参保人的性别和年龄调整健康计划支付，很可能仍会继续如此，因为这种选择是基于难以观察到的参保人特征，例如对医疗保健的偏好和健康状况。
