Competition and Defaults in Online Search (with Francesco Decarolis and Filippo Paternollo) [ American Economic Journal: Microeconomics (2025)] {VOX Columns}
Sharing Economy Platforms in the Face of Crises:A Conceptual Framework (with Paul Belleflamme and Anaïs Périlleux) [ Sustainability (2025)]
Self-Preferencing in Adjacent Markets [ Competition Policy International (2025)]
Regulating Online Search in the EU: From the Android Case to the Digital Markets Act and Digital Services Act (with Francesco Decarolis) [ International Journal of Industrial Organization (2023)]
Do Lower Search Costs Benefit Intermediaries? [Review of Industrial Organization (2023)]
Competition, Defaults, and Antitrust Remedies in Digital Search (with Francesco Decarolis) [ Competition Policy International (2022)]
Dominating Ancillary Product Markets via Self-Preferencing [CRESSE- CPI Young Researchers Awards 2024][EODS Awards, University of Pennsylvania] {EODS Blog}
Abstract: On most platforms, transactions between buyers and sellers require ancillary products. Examples include iOS developers requiring electronic payment systems, YouTubers requiring advertising technology, or Amazon sellers requiring automatic pricing tools. This paper studies a scenario where a firm operates a monopoly platform while facing competition in the ancillary product market. The platform practices self-preferencing by reducing sellers' profit if they use competing ancillary products. I show that when self-preferencing is profitable for the platform, sellers always benefit, while buyers may be worse off under certain conditions. Empirical evidence from a recent antitrust case against Google supports the theoretical findings.
Post-Merger Strategies of Multiplatform Monopolies (with Filomena Garcia) [Best Digital Economies Paper Award in Conferência Digitalização na Economia]
Abstract: Mergers and acquisitions are on the rise in platform industries, leading to an increase in market power. This paper investigates the impact of post-merger strategies on the market. We develop a model where two different platforms coexist and a merger is under consideration. We then analyze various post-merger strategies, including platform integration and advanced pricing tactics like bundling. Our findings indicate that, in most cases, a multiplatform monopoly resulting from the merger reduces users' overall surplus, especially when bundling is employed. However, when users multihome and the platforms are highly different, a multiplatform monopoly without bundling can result in a higher surplus compared to a competitive market. We provide antitrust guidance on mergers of horizontally differentiated platforms, taking into consideration post-merger strategies.
Abstract: Existing research states that an increase in interest rates discourages better borrowers, resulting in a higher default rate. We observe the opposite from analyzing a recent interest adjustment on a peer-to-peer lending platform: borrowers defaulted less after a higher interest rate. To understand the underlying driving force of the borrowers’ behaviors, we model a borrower’s decision to take up the loan and her per-period payment strategy in a dynamic model after taking up the loan. We prove that unobserved default risk alone cannot explain such a data pattern. To rationalize such a counterintuitive data pattern, we introduce another imperfect information besides the borrowers’ default risk. Specifically, the borrowers’ perceptions of payment could differ; some are aware of the prepayment option, but some are inattentive to this option. Such behavior bias helps rationalize the counterintuitive pattern because a rising interest rate discourages naive borrowers from taking up loans more than their sophisticated counterparts. At the same time, naive borrowers’ default rate is higher than sophisticated borrowers due to the prepayment option.
Regulating Digital Advertising: Self-Preferencing in the Ad Tech Stack (with Francesco Decarolis)
Abstract: Dominant platforms expanding and practicing self-preferencing across various sectors have been pervasive in digital markets. This study assesses the first emerging regulation aimed at curbing Google’s self-preferencing within the French display advertising market (the, so-called, ad tech stack). Through an empirical analysis, we show surprising patterns: in the short run after the data-sharing mandate imposed on Google by the French Competition Authority, we find a substantial reduction of over 300 advertisers on French popular websites and a weekly revenue loss exceeding $95,000 for publishers. Using a simple theoretical model, we then explore the potential mechanisms and determinants influencing the regulatory impact. Our main insight is that the regulatory intervention, which was aimed exclusively at the publishers’ side of the market, backfired on publishers and advertisers due to the features of the network externalities in this market and the relative quality of Google compared to its rivals.
Platform Management (with Paul Belleflamme and Filomena Garcia)
Abstract: The rapid development of information technology enables digital platforms to employ a wider set of fee instruments and assume additional roles beyond being a pure marketplace. In this paper, we investigate these two aspects and their interactions. Employing a unified framework, we demonstrate that there are multiple choices of fee combinations that allow the platform to achieve optimal profit. Second, by evaluating the impact of fee instruments on the platform’s control over user participation, we clarify the relationships among them and propose an innovative method to categorize platforms. Third, we highlight that a platform’s managerial decision to take on additional roles in the digital market is jointly determined by its available fee instruments and how the additional role affects its market.