Because firms’ takeover motives are unobservable to investors, mergers are only partially anticipated and often appear as mixed blessings for acquirers. I construct and estimate a model to study the causes and consequences of bid anticipation and information revelation in mergers. Controlling for the market’s reassessment of the acquirer’s stand-alone value, I estimate that acquirers gain 4% from a typical merger. The total value of an active merger market averages 13% for acquirers, part of which is capitalized in their pre-merger market values. My model also explains the correlation between announcement returns and firm characteristics, as well as the low predictability of mergers.

If opportunistic acquirers can buy targets using overvalued shares, then there is an inefficiency in the merger and acquisition (M&A) market: the most overvalued rather than the highest-synergy bidder may buy the target. We quantify this inefficiency using a structural estimation approach. We find that the M&A market allocates resources efficiently on average. Opportunistic bidders crowd out high-synergy bidders in only 7% of transactions, resulting in an average synergy loss equal to 9% of the target’s value in these inefficient deals. The implied average loss across all deals is 0.63%. Although the inefficiency is small on average, it is large for certain deals, and it is larger when misvaluation is more likely. Even when opportunistic bidders lose the contest, they drive up prices, imposing a large negative externality on the winning synergistic bidders.