Defining a Relevant Market for Digitals Platforms: Theory and Regulatory Practice

On many markets digital platforms hold a dominant position, which requires an assessment of their actions from an antitrust point of view. To do this, it is necessary to assess the boundaries of the relevant market, which is associated with a number of methodological problems. Firstly, due to the presence of the phenomenon of zero prices, traditional methodology can produce incorrect results. Secondly, digital platforms function on multisided markets and thus it is required to define market boundaries for each group of agents.In this article theoretical approaches to assessing market boundaries for digital platforms and antitrust practice are considered. The paper dwells on the theoretical and methodological aspects of the definition of market boundaries for digital platforms and how these definitions turn into antitrust practices and influence the decisions made by regulatory authorities. The author argues that it's the market boundaries' definition that was the key influence on many antitrust proceedings against digital platforms. In addition, methodological approaches to determining market boundaries of Russian and foreign antimonopoly regulators are compared. Based on this analysis, an approach to determining market boundaries for digital platforms is proposed.