Moral hazard in insurance, value-based cost sharing, and the benefits of blissful ignorance.

The conventional theory of optimal coinsurance rates for health insurance with moral hazard indicates that coinsurance should vary with the price responsiveness or price-elasticity of demand for different medical services. An alternative theory called "value-based cost sharing" indicates that coinsurance should be lower for services with higher (marginal) benefits relative to costs. This paper reconciles the two views. It shows that, if patient demands are based on correct information, optimal coinsurance is the same under either theory. If patient demands differ from informed demands, optimal coinsurance depends both on information imperfection and price responsiveness. Value-based cost sharing can be superior to providing information (even if the cost of information is minimal) when patient demands fall short of informed demands. An extended numerical example illustrates these points.