There is a growing concern that U.S. merger control may have been too lenient, but empirical evidence remains limited. Event studies have been used as one method to acquire empirical insights into the competitive effects of mergers. However, existing work suffers from strong identifying...

Anticompetitive mergers increase competitors' profits, since they reduce competition. Using a model of endogenous mergers, we show that such mergers nevertheless may reduce the competitors' share-prices. Thus, event-studies can not detect anti-competitive mergers.