Abstract Since the late 1990s, over 75% of US industries have experienced an increase in concentration levels. We find that firms in industries with the largest increases in product market concentration show higher profit margins and more profitable mergers and acquisitions deals. At the same time, we find no evidence for a significant increase in operational efficiency. Taken together, our results suggest that market power is becoming an important source of value. These findings are robust to the inclusion of (i) private firms; (ii) factors accounting for foreign competition; and (iii) the use of alternative measures of concentration. We also show that the higher profit margins associated with an increase in concentration are reflected in higher returns to shareholders. Overall, our results suggest that the US product markets have undergone a shift that has potentially weakened competition across the majority of industries.

Although complementarity between products and/or technologies of bidders and targets is considered a key driver of M&A deals, many observed mergers are inefficient: Complementarity gains in actual mergers are lower than the gains that could have been obtained were the targets acquired by different bidders. In this paper we propose a possible reason for the existence of inefficient mergers, which is based on search and information frictions. Our model examines three such frictions: target’s obsolescence risk, difficulties in evaluating complementarity gains, and competitive interaction among potential bidders in output markets. We test the model’s predictions using two established measures of complementarity gains in mergers: product similarity and technological overlap. Both sets of tests indicate that the degree of inefficiency in observed M&As is related to targets’ and bidders’ characteristics in ways consistent with the model’s predictions. More generally, our results suggest that search and value discovery are important determinants of merger outcomes.