IMF Working Papers

We develop a search-based theory of mergers and acquisitions with heterogeneous firms and endogenous search complementarities. We use this model to understand how merger incentives and the firm size distribution interact. In equilibrium, search costs and entry rates determine search intensities and shape the distribution of market power. We derive the law of motion of the firm size distribution, provide closed-form solutions, and solve for endogenous search efforts. Finally, we derive the aggregate welfare function and show how our framework can be used to simulate the impact of various antitrust policies. In particular, antitrust policy can have large effects on welfare due to the existence of multiple equilibria.