We quantify the impact of merger activity on productive efficiency. We develop and calibrate a dynamic industry-equilibrium model that features mergers, entry, and exit by heterogeneous firms. Mergers affect productivity directly through realized synergies, and indirectly through firms’ incentives to enter or exit the industry. Merger activity increases average firm productivity by 4.8%, of which 4.1% reflects the accumulation of synergies, and 0.7% the interaction between merger options and firms’ entry and exit decisions. We show that ignoring the implications of merger activity for public policies that promote entry can reverse the expected impact of these policies on productivity.

We evaluate empirically two sources of large takeover premiums: preemptive bidding and target resistance. We develop an auction model that features costly sequential entry of bidders in takeover contests and encompasses both explanations. We estimate the model parameters by simulated method of moments for a sample of US takeovers. Our estimates imply that target resistance explains the entire magnitude of the premium in 74% of successful single-bidder contests. Simulation experiments show that initial bidders have, on average, a higher valuation for the target than rival bidders, so that a relatively low initial bid is sufficient to deter a rival from entry.