Digital platforms operate in multisided markets providing services through the internet to two or more distinct groups of users, between which there are indirect network effects. Direct network effects are frequently present within each group. Therefore, online platforms usually present both...

Market definition, a concept that has long served to structure competitive analysis, is under assault from theoreticians who object to the inability of the standard analysis to define a market compatible with their models of unilateral effects. Although these unilateral models have not been...

The last couple of years have seen an increasing interest in critical loss analysis, both, in academia and in practice. This development is documented by various research papers, high-level exchanges between antitrust experts as well as an increasing number of case decisions – in the United...

In a recent series of articles, I argue that the market definition/market share paradigm should be abandoned entirely. Among my central claims are that: (1) as a matter of economic logic, there exists no valid way to infer market power from the market shares in redefined (non-homogeneous-goods)...

Market definition has long held a central place in competition law. This entry surveys recent analytical work that has called the market definition paradigm into question on a number of fronts: whether the process is feasible, whether market share threshold tests are coherent, whether the...

Monopolization, in the United States, and abuse of dominance, in the European Union, embody different philosophies about how best to police single firm conduct in competition law. Surprisingly, their disagreement ends at market definition. Both doctrines define relevant markets by similar...

Surging interest in antitrust enforcement is exposing, once again, the difficulty of defining relevant markets. Past decades have witnessed the invention of many tests for defining markets, but little progress has been made, or even attempted, at reconciling these different tests. Modern market...

This is a survey of the economic principles that underlie antitrust law and how those principles relate to competition policy. We address four core subject areas: market power, collusion, mergers between competitors, and monopolization. In each area, we select the most relevant portions of...

This paper considers the effect of taxes on the definition of relevant markets in antitrust analysis by examining various measures used within the hypothetical monopoly test. We show that the use of net margins (between producer prices and marginal cost) is a proper correction, but that it is...