Optimal Ex Post Risk Adjustment in Markets with Adverse Selection

This paper studies general health insurance markets. It proposes an ex post risk adjustment scheme that discourages risk selection and promotes efficient competition. Under the proposed risk adjustment scheme, the regulator engages in transfers that are conditional on the ex post profits of insurers. The risk adjustment scheme is entirely budget balanced -- as it does not call for government subsidies -- and requires the regulator to hold minimal information to implement it. Equilibrium exists and each equilibrium allocation is efficient in any environment with a finite number of types and states even if single-crossing is not satisfied