This study aims at characterizing the optimal regulation of risky activities when risk assessment is subjective as a result of ambiguity on the probability of an accident. The attitudes toward ambiguity held by stakeholders form subjective risk perceptions, which substantially affect the optimal...

Evaluating network effects and two-sidedness is critical for merger control in the digital economy.To examine the impact of network effects on the welfare properties of mergers, this study analyzes a model of multiproduct-firm oligopoly with firm-level direct and indirect network externalities...

Consumer multi-homing is considered to be critical for competition policy regarding digital platforms. To assess the role of consumer multi-homing in competition policy toward platforms, we develop a new framework that embeds consumer multi-homing in two-sided market into the otherwise standard...

This paper proposes a new model of imperfect competition of ad-sponsored media, which can sell "free" products, for a merger analysis applicable to the mobile app industry. To analyze developers’ monetizing with both price and advertising in an app, we consider a consumer who faces both budget...

We investigate the impact of search order distortion by a vertically integrated platform that intermediates the products of a third-party seller as well as its own product. The platform can steer consumers to search for its own product first. We show that the effects of search order distortion...

This study presents a static model of media bias with a representative consumer, where a news source decides whether to grant information access to each media outlet. We show that the effect of a news source depends on the market structure. It does not distort a monopolistic media outlet’s...

In platform markets, consumers often choose which platform to use for making a bundle of transactions with sellers rather than for each transaction. Based on a competition-in-utility framework, I analyze the impact of such usage lock-in on platform competition. Usage lock-in allows platforms to...

This paper presents an examination of issues related to liability for harm to consumers caused by goods sold by third-party sellers on e-commerce platforms. A model of platform design is presented in which a platform chooses its liability design, specifying the percentages of consumer harm that...