Switching costs and network effects bind customers to vendors if products are incompatible, locking customers or even markets in to early choices. Lock-in hinders customers from changing suppliers in response to (predictable or unpredictable) changes in efficiency, and gives vendors lucrative ex...

This chapter surveys empirical models of market structure. We pay particular attention to equilibrium models that interpret cross-sectional variation in the number of firms or firm turnover rates. We begin by discussing what economists can in principle learn from models with homogeneous...

Recently there has been a notable increase in interest in antitrust law in much of the world. This chapter discusses antitrust policy toward horizontal mergers, the area of antitrust that has seen some of the most dramatic improvements in both economic tools and the application of economics in...

This chapter reviews the literature which has developed around the ‘bounds approach’ to market structure over the past fifteen years. The focus of this literature lies in explaining cross-industry differences in concentration, and in the size distribution of firms. One of the main ideas...

This paper reviews a framework for numerically analyzing dynamic interactions in imperfectly competitive industries. The framework dates back to Ericson and Pakes [1995. Review of Economic Studies 62, 53–82], but it is based on equilibrium notions that had been available for some time before,...

This chapter reviews recent theoretical work on the design of regulatory policy, focusing on the complications that arise when regulated suppliers have better information about the regulated industry than do regulators. The discussion begins by characterizing the optimal regulation of a monopoly...