I use a 2010 non-profit hospital merger in Ohio to study the effect of market concentration on market outcomes. Using the Synthetic Control Method and Truven MarketScan data, I document three findings. First, courts are lenient to non-profit mergers, and I cast doubt on this practice by showing that the studied merger led to a 123% increase in the payments for inpatient childbirth services. Second, I provide the first empirical evidence for the conjecture that mergers increase out-of-pocket payments and reduce the utilization of care. Last, I show that the effect of market power on market outcomes is asymmetric: the increase in payments and welfare loss created by a merger persist after the merger is rescinded. Thus, even successful FTC challenges may not revert the effect of harmful mergers, and it is essential to deny such mergers before they proceed.

我使用 2010 年俄亥俄州非营利性医院合并来研究市场集中度对市场结果的影响。使用综合控制方法和 Truven MarketScan 数据，我记录了三个发现。首先，法院对非营利性合并持宽容态度，我对这种做法表示怀疑，因为所研究的合并导致住院分娩服务费用增加了 123%。其次，我为合并增加了自付费用并降低了护理利用率的猜想提供了第一个经验证据。最后，我表明市场支配力对市场结果的影响是不对称的：在合并取消后，合并造成的支付和福利损失的增加仍然存在。因此，即使是成功的 FTC 挑战也可能无法逆转有害合并的影响，