Disability insurance and optimal income taxation

This paper studies the design of disability insurance scheme when agents differ in their privately known productivity. We extend the Diamond and Mirrlees (1978) two period model to allow for agents differing ex-ante in their productivity and characterize the optimal nonlinear tax transfer that maximizes a utilitarian welfare function when per-period earnings and age are observable while individuals' productivity and health status are not observable. We show that the induced tax/benefit scheme should exhibit a marginal income tax that decreases with age for some agents. A marginal subsidy on the young high productive income may be desirable. While the disability scheme always involves the old low productive agents to be indifferent between working and claiming disability benefits, this result is not always true for the old high productive agents.