Are Health Insurance Markets Competitive?
研究利用1998-2005年大型多地点企业的健康计划数据，发现保险公司对利润更高的企业收取更高保费，且集中市场中的企业保费涨幅更大，表明保险公司在多地行使市场力量。
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.