We examine whether and to what extent consolidation in the US health insurance industry has contributed to higher employer-sponsored insurance premiums. We exploit the differential impact across local markets of a national merger of two insurers to identify the causal effect of concentration on...

This paper examines hospital responses to changes in diagnosis-specific prices by exploiting a 1988 policy reform that generated large price changes for 43 percent of Medicare admissions. I find hospitals responded primarily by "upcoding" patients to diagnosis codes with the largest price...

To gauge the competitiveness of the group health insurance industry, I investigate whether health insurers charge higher premiums, ceteris paribus, to more profitable firms. Such "direct price discrimination" is feasible only in imperfectly competitive settings. Using a proprietary national...