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

We provide a possible explanation for the empirical puzzle that mergers often reduce profits, but raise share prices. If being an "in- sider" is better than being an "outsider", firms may merge to preempt their partner merging with a rival. The insiders' stock market value is increased, since the risk of becoming an outsider is eliminated. These results are derived in an endogenous-merger model, predicting the conditions under which mergers occur, when they occur, and how the surplus is shared.