The Evolution (and Devolution) of Market Structure Reasoning

Abstract

Since the late 1960s, U.S. federal antitrust agencies have enjoyed the opportunity, and tacit approval, to gently guide merger law in the form of published merger guidelines, statements, and revisions. The Agencies have contributed much to merger law in this way but have often trembled to prune it. As market structure reasoning has been allowed to grow more of less untended since 1968, decades of growth, overgrowth, and decay are now on display in the variety of structural inferences in the 2023 Merger Guidelines. This chapter surveys the evolution and devolution of market structure reasoning in the Merger Guidelines, starting in 1968 and ending with the insights and errors of the 2023 update.

Keywords: merger guidelines, market structure, presumption

JEL Classification: K21, L40