Hospital Network Competition and Adverse Selection: Evidence from the Massachusetts Health Insurance Exchange
利用马萨诸塞州保险交易所数据，研究发现覆盖顶级“明星”医院的保险计划面临严重的逆向选择，消费者对明星医院的忠诚导致高支出，即使有风险调整，保险公司仍有强烈动机排除这些医院。
Health insurers increasingly compete on their networks of medical providers. Using data from Massachusetts’s insurance exchange, I find substantial adverse selection against plans covering the most prestigious and expensive “star” hospitals. I highlight a theoretically distinct selection channel: consumers loyal to star hospitals incur high spending, conditional on their medical state, because they use these hospitals’ expensive care. This implies heterogeneity in consumers’ incremental costs of gaining access to star hospitals, posing a challenge for standard selection policies. Along with selection on unobserved sickness, I find this creates strong incentives to exclude star hospitals, even with risk adjustment in place.