This Chapter provides a survey of the economics literature on multi-sided platforms with particular focus on competition policy issues, including market definition, mergers, monopolization, and coordinated behavior. It provides a survey of the general industrial organization theory of...

This paper investigates how the tying of complementary products can be used to preserve and extend monopoly positions. We first show how a firm that is a monopolist of a product in the current period can use tying to preserve its monopoly position in future periods. We then show using related...

We study an economy in which consumers and merchants (sellers) interact on a two-sided platform. Consumers can share data about their tastes for different varieties of a single good with the platform which in turn sells this data to merchants. Data sharing increases gains from trade by improving...

This paper investigates consumer switching costs in the context of health insurance markets, where adverse selection is a potential concern. Though previous work has studied these phenomena in isolation, they interact in a way that directly impacts market outcomes and consumer welfare. Our...

I use the Medicare Part D prescription drug insurance market to examine the dynamics of firm interaction with consumers on an insurance exchange. Enrollment data show that consumers face switching frictions leading to inertia in plan choice, and a regression discontinuity design indicates...

I take advantage of regulatory and pricing dynamics in Medicare Part D to empirically explore interactions among adverse selection, switching costs, and regulation. I first document novel evidence of adverse selection and switching costs within Part D using detailed administrative data. I then...

I estimate the relative magnitudes of worker switching costs and how much the employer switching of experienced engineers responds to outside wage offers. Institutional features imply that voluntary turnover dominates switching in the market for Swedish engineers from 1970--1990. I use data on...

We study theoretically and empirically how consumers in an individual private long-term health insurance market with front-loaded contracts respond to newly mandated portability requirements of their old-age provisions. To foster competition, effective 2009, German legislature made the...

Although doctors and hospitals own their patients' medical records, state and federal laws require that they provide patients with a copy at "reasonable cost." We examine the effects of state laws that cap the fees that doctors and hospitals are allowed to charge patients for a copy of their...

We solve a portfolio choice problem when expected returns, volatilities and trading-costs follow a regime-switching model. The optimal policy trades towards an aim portfolio given by a weighted-average of the conditional mean-variance portfolios in all future states. The trading speed is higher...