Event studies in merger analysis : review and an application using U.S. TNIC data

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 assumptions, unreliable competitor identification or small samples. After reviewing the use and challenges of event studies in merger analysis, I use a novel application of Hoberg-Phillips (2010, 2016) Text-Based Network Industry Classification (TNIC) data to readily proxy a ranking of competitors to 1,751 of the largest U.S. mergers between 1997 and 2017. I document that following a merger announcement, the most likely competitors experience on average an abnormal return of around one percent. These abnormal returns are also associated with concerns of market power, which suggests that results are at least in part driven by an anticipation of anti-competitive effects, and hence insufficient merger control.