One of the principal anticompetitive concerns raised in the context of horizontal mergers is the potential for the merging parties to have the incentive and the ability to increase prices post-transaction. While there are well-established methodologies that merger practitioners routinely use to assess such concerns, evaluating firms’ pricing incentives in the context of horizontal multi-sided platform mergers is still an emerging area of active research. The relatively sparse understanding of this issue does not mean it is not a significant one.

With the spectacular growth of the technology sector in the last decades and the intense mergers-and-acquisitions activity in this sector, antitrust authorities in the United States and in other jurisdictions around the globe have dedicated more and more resources to the control and enforcement of platform mergers. Indeed, the 2023 Merger Guidelines devote an entire subsection, Guideline 9, to explaining in detail that “when a merger involves a multi-sided platform,” the U.S. Department of Justice and the Federal Trade Commission are committed to “examin[ing] competition between platforms, on a platform, or to displace a platform.”

This article reviews the tools available in the economics literature for assessing the potential for anticompetitive pricing incentives in the context of horizontal multi-sided platform mergers. In the last decades, Gross Upward Pricing Pressure Indices (hereinafter “GUPPIs”) developed by economists have become the standard practice for measuring pricing incentives potentially arising from mergers in one-sided markets. However, these GUPPIs for one-sided markets are not suitable for analyzing multi-sided platform mergers, given the necessity of taking into account an array of complexities brought about by the existence of interactions between different sides of a multi-sided market. This is a challenging task, and thus not many papers in the economics literature have taken on the issue.

The goal of this article is to review these papers, to summarize the intuition behind these GUPPIs, and to outline the unique challenges associated with applying them to multi-sided platform mergers. We conclude by observing that more comprehensive approaches will be required to further broaden the understanding of channels through which incentives for unilateral price increases may arise in the context of multi-sided platform mergers.