ARTICLE: What Structural Presumption?: Reuniting Evidence and Economics on the Role of Market Concentration in Horizontal Merger Analysis Skip over navigation
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Copyright (c) 2016 University of Iowa (Journal of Corporation Law)
The Journal of Corporation Law

ARTICLE: What Structural Presumption?: Reuniting Evidence and Economics on the Role of Market Concentration in Horizontal Merger Analysis

Winter, 2016

Journal of Corporation Law

42 Iowa J. Corp. L. 403


Sean P. Sullivan*


I. Introduction

The structural presumption is an important but contentious proposition in the antitrust law of horizontal mergers. It stands for the typical illegality of mergers that would combine rival firms with large shares of the same relevant market. The structural presumption is so named because the likely anticompetitive effects of such mergers are in some sense presumed to follow from the change in market structure involved in such consolidations. In one form or another, the structural presumption has undergirded all antitrust analysis of horizontal mergers since at least the early 1960s.

Today, the structural presumption is a topic of significant debate. Though well entrenched in legal precedent, the validity and normative desirability of this proposition are increasingly questioned. Proponents argue that mergers leading to strongly concentrated markets tend to lessen competition and harm consumers. On this basis, they support a presumption that mergers leading to highly concentrated markets should generally be prohibited, even if specific theories of competitive harm are not brought forward by the party seeking relief. 1 Opponents of the proposition argue that market structure should not be treated as determinative of the competitive consequences of a merger. They propose to eliminate any presumption of harm based on market concentration evidence and would generally require specific theories of harm to be raised as the basis for relief. 2

As things stand, consensus is not forthcoming. Across numerous academic papers, 3 conferences, 4 formal speeches, 5 informal commentaries, 6 administrative statements, 7 and judicial opinions, 8
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