Measuring the Welfare Effect of Entry in Differentiated Product Markets: The Case of Medicare HMOs

Should governments subsidize entry to promote competition? In general, theory models cannot determine whether entry under the free-entry condition is socially excessive, optimal, or insufficient. In this paper I propose an empirical framework to evaluate welfare consequences of policy intervention through entry in differentiated product markets, with a case study of the US Medicare HMO market. In endogenizing firms' entry-exit decision, a technical breakthrough is to explicitly incorporate firm heterogeneity by employing a sequential move game. This enables us to exploit detailed firm level data and makes policy simulations relevant. I find no evidence of socially excessive entry. The government may achieve higher social welfare by expanding the program.