Market Structure after Horizontal Mergers: Evidence from the Banking Industry.

Antitrust agencies use measures of market structure to evaluate the likely competitive effects of proposed mergers, but little is known about how measures of market structure change over time, particularly after consummation of mergers and acquisitions. This paper analyzes the changes in market structure 3 and 5 years after mergers in the US banking industry. Our analysis suggests that concentration decreases and the number of banks increases in banking markets where mergers resulted in high concentration levels. In markets where the level of concentration changed by a relatively large amount, our findings are more ambiguous, as the level of concentration decreases, but no effect is found on the number of competitors. [ABSTRACT FROM AUTHOR]