Proposed Mergers Where Efficiencies Are Needed Most Might Be the Least Likely to Deliver Them

Mergers are commonly evaluated by weighing their expected market power effects against any efficiency gains they create. The larger the market power effect of a proposed merger, the larger must be any efficiencies for it to raise social welfare. We show selection into merger proposal distorts the observed relationship between market power and efficiency effects. Even if market power and efficiency gains are independent (or even positively correlated) across all potential mergers, they will generally be negatively related among proposed mergers. This is because parties propose to merge only if the merger’s expected profitability exceeds a threshold, so the underlying components of profitability become substitutes in clearing that hurdle. It does not rely on managerial bias, behavioral frictions, or strategic misrepresentation. We demonstrate this negative correlation is present under very general conditions when the two effects are uncorrelated among all mergers. We also characterize conditions where this still holds even in the presence of positive underlying correlations and firms’ uncertainty about their own merger’s profitability. Policies that might raise the selection hurdle for proposed mergers do not alleviate the negative correlation; indeed, they would exacerbate it. Our analysis has direct implications for interpreting empirical merger retrospectives and for evaluating efficiency defenses in antitrust policy.