Coinsurance vs. Copayments: Reimbursement Rules for a Monopolistic Medical Product with Competitive Health Insurers

This paper studies a market for a medical product in which there is perfect competition among health insurers, while the good is sold by a monopolist. Individuals differ in their severity of illness and there is ex post moral hazard. We consider two regimes: one in which insurers use coinsurance rates (ad valorem reimbursements) and one in which insurers use copayments (specific reimbursements). We show that the induced equilibrium with copayments involves a lower producer price and a higher level of welfare for consumers. This results provides strong support for a reference price based reimbursement policy.