Simulating Partial Asset Divestitures to 'Fix' Mergers

In this paper, we apply and extend merger simulation methodology to analyze the effectiveness of partial divestitures as a 'fix' to remedy the possible anticompetitive effects of horizontal mergers. Typically, antitrust agencies require merging firms to divest assets so that the status quo before the merger is restored, that is, they favor a 'full divestiture'. We focus on the effectiveness of a partial divestiture as an antitrust remedy (where a subset of products owned by the merging firms is spun off). Although this is not the type of full divestiture favored by antitrust agencies, we argue here that a partial divestiture could leave consumers better off after the merger than they were before - under certain conditions. Using a real-world example, we show how divesting a relatively close substitute creates competition that offsets the anticompetitive effects of combining products that are relatively distant substitutes. This result stands even when the divestee is moderately inefficient.