Incomplete risk adjustment and adverse selection in the German public health insurance system

The German statutory health insurance market was exposed to competition in 1996. To avoid adverse selection, a prospective risk compensation scheme was introduced in 1994. Due to their low contribution rates, company-based sickness funds were able to attract a lot of new members. We analyze – using data from the German Socio- Economic Panel – the determinants of these transitions from 1995 to 2000. By estimating a simultaneous two equation system, we find that health status positively, and significantly, affects the probability of changing to a company-based sickness fund, especially after controlling for age. Thus the risk compensation scheme does not fully control for the health status of the changers. Consequently, the comparative advantages of company-based funds will increase over time. This observation provides evidence for the standard Rothschild-Stiglitz separating equilibrium.