The predictors of HMO enrollee populations: results from a national sample.

This study is the first to use a national data set to analyze the kinds of people who enroll in HMOs versus conventional insurance, whether or not they faced a choice. Our explanatory variables include two measures of health: reported health status and number of medical conditions. Although neither variable proved to be significant, our coefficient estimates suggest that ill health increases the probability of being enrolled in an HMO, as does larger family size. The income elasticity of HMO enrollment is -.64, which suggests that families of modest means are a natural clientele of HMOs.