Competition in Health Insurance Markets
记录了美国商业、Medicare Advantage和Medicaid市场的集中度，并研究逆向选择如何与市场势力相互作用影响保费、计划设计和消费者福利，实证表明保险公司合并推高保费。
The United States relies primarily on private health insurance markets, yet these markets are highly concentrated and becoming more so over time. We document concentration across commercial, Medicare Advantage, and Medicaid markets. We then examine how asymmetric information—particularly adverse selection—interacts with market power to shape premiums, plan design, and consumer welfare. Empirical evidence confirms that insurer consolidation raises premiums. We discuss how antitrust enforcement, risk adjustment, regulation, and informational interventions shape competition and consumer welfare in these markets.