David Glasner and Sean P. Sullivan on ‘The Logic of Market Definition’ (forthcoming) Antitrust Law Journal

This paper,available here , is not technically about merger control, but it is as relevant here as in any other competition topic – and it fits nicely with wider discussions of market power and market entry, which, as we have seen in past weeks, are common in merger control. While the usefulness of, and methodologies concerning market definition would seem to be well established, in practice both are actively questioned. Some have even argued that market definition is unnecessary in competition law. While this argument is not new, Louis Kaplow has recently advanced this thesis with a particularly pointed argument that: (1) market definition serves no role except to produce market shares, (2) market shares are poor measures of market power, and (3) antitrust would be better served by ignoring market shares and trying to assess market power from estimates of residual-demand curves and the like instead. The goal of this paper is to trace the internal logic of market…

Tommaso Valletti and Hans Zenger on ‘Mergers with differentiated products: Where do we stand?’

This paper, available here, provides an overview of the state of economic analysis of unilateral effects in mergers with differentiated products. It discusses both static and dynamic competition. Section 2 focuses on price competition and discusses the calibration of unilateral effects using diversion-based tools such as upward pricing pressure. One of the most prominent developments of the past decades was to put closeness of substitution at the heart of unilateral effects analysis. It is well known that market shares can be off the mark in trying to account for consumers’ heterogeneous switching patterns between differentiated products. When robust data is available, it is therefore more sensible to assess competitive overlaps directly via diversion ratios than to rely on market shares as an imperfect proxy. Obtaining an estimate of diversion is feasible in many, though far from all, significant mergers (e.g., through switching data, bidding data, customer surveys, event studies or demand estimation). While diversion ratios provide a good indication of…