Competitive Harm from Vertical Mergers

The antitrust enforcement Agencies’ 2020 Vertical Merger Guidelines (VMGs) introduce a nontechnical application of bargaining theory into the competitive assessment of vertical acquisitions. This bargaining theory has much in common with the theory of unilateral effects that is applied to horizontal mergers. The VMGs focus on post-merger price increases requires consideration of a vertical merger’s role in eliminating double marginalization (EDM). The problem occurs when two bargaining firms both have market power but are unable to coordinate their output. Assessing EDM bundles two themes that Ronald Coase developed in his two most well-known articles: “The Nature of the Firm” and “The Problem of Social Cost”. The first argued that the boundaries of a firm are determined by the firm’s continuous search to minimize costs. The second argued that two traders in a well-functioning market will achieve the joint-maximizing solution. Anti-interventionists rely heavily on Coasean arguments that unless high transaction costs get in the way firms will bargain to joint maximizing results. If that is true, then double marginalization will rarely provide a defense to a vertical merger. The law of vertical mergers deals largely with firms that transact with one another routinely, in legally enforceable buy-sell relationships. In a well-functioning vertical market durable double marginalization should be rare.