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 database of health plans offered by a sample of large, multisite firms from 1998–2005, I find firms with positive profit shocks subsequently face higher premium growth, even for the same health plans. Moreover, within a given firm, those sites located in concentrated insurance markets experience the greatest premium increases. The findings suggest health care insurers are exercising market power in an increasing number of geographic markets.

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 increases. This response was particularly strong among for-profit hospitals. I find little evidence hospitals increased the volume of admissions differentially for diagnoses subject to the largest price increases, despite the financial incentive to do so. Neither did they increase intensity or quality of care in these diagnoses, suggesting hospitals do not compete for patients at the diagnosis level.

The Affordable Care Act has engendered significant changes in the design of health insurance products. We examine the “narrowness” of hospital networks affiliated with plans offered in the first year of the marketplaces. Using data from Texas, we find limited evidence of a tight link between pricing and a simple measure of network breadth, or a more complex measure of network value derived from a logit model of hospital choice. The state's largest insurer priced its narrow networks at a fairly constant discount relative to its broad networks, notwithstanding significant variation in its broad-narrow gap across geographic markets in Texas.

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 premiums. Using data for large groups, we estimate premiums in average markets were approximately seven percentage points higher by 2007 due to increases in local concentration from 1998–2006. We also find evidence consolidation facilitates the exercise of monopsonistic power vis-à-vis physicians, leading to reductions in their absolute employment and earnings relative to other healthcare workers. JEL: G22, I13

An Individual Health Plan Exchange: Which Employees Would Benefit and Why? by Leemore Dafny, Katherine Ho and Mauricio Varela. Published in volume 100, issue 2, pages 485-89 of American Economic Review, May 2010