Optimal Risk-Sharing and Deductables in Insurance

Risk-sharing in insurance is analyzed, with a view towards explaining the prevalence of deductibles. First we introduce, in a modern setting, the main concepts of the theory of risk-sharing in a group of agents. This theory we apply to the risk-sharing problem between an insurer and an insurance customer. We motivate the development through simple examples, illustrating some of the subtle points of this theory. In order to deduce deductibles endogenously, not explained in the neoclassical model, we separately introduce (i) the insurable asset as a decision variable, (ii) administrative costs, and (iii) moral hazard, and illustrate by examples