Why mergers reduce profits and raise share prices: A theory of preemptive mergers

We explain the empirical puzzle why mergers reduce profits and raise share prices. If being an “insider” is better than being an “outsider,” firms may merge to preempt their partner merging with a rival. The stock-value of the insiders is increased, since the risk of becoming an outsider is eliminated. We also explain why shareholders of targets gain while acquirers typically break even. These results are derived in an endogenousmerger model, predicting the conditions under which mergers occur, when they occur, and how the surplus is shared.