Horizon Effects and Adverse Selection in Health Insurance Markets
We study how increasing contract length affects adverse selection in health insurance markets. Although health risks are persistent, private health insurance contracts in the United States have short, one-year terms. Short-term, community-rated contracts allow patients to increase their coverage only after risks materialize, which leads to market unraveling. Longer contracts ameliorate adverse selection because both demand and supply exhibit horizon effects. Intuitively, longer horizon risk is less predictable, thus elevating demand for coverage and lowering equilibrium premiums.