Trade associations and collusion among many agents: evidence from physicians
研究某市大多数妇科医生通过行业协会集体谈判提高费率，在谈判失败后联合终止合同并设定最低价格，发现实际价格与纳什-伯特兰价格一致，最低价格几乎没有约束力，这些行为确保了协会稳定并增加了利润。
Abstract We study a recent case where most gynecologists in one city formed a trade association to bargain for better rates with insurance companies. After unsuccessful negotiations, the physicians jointly terminated their insurer contracts and set a minimum price. We find that subsequent realized prices coincided with Nash‐Bertrand prices, and that the minimum price was barely binding. We show that these actions ensured the association's stability and increased profits. Our findings shed light on the role of trade association in collusion among a large number of heterogeneous agents, and provide insights for the antitrust analysis of trade associations.