Market definition and market power are central features of competition law and practice but pose serious challenges. On one hand, market definition suffers decisive logical infirmities that render it infeasible, unnecessary, and counterproductive, and the practice of stating market power...

Market definition is essential to merger analysis. Because no standard approach to market definition exists, opposing parties in antitrust cases often disagree about the extent of the market. These differences have been particularly relevant in the hospital industry, where the courts have denied...

Competition in many important industries centers on investment in intellectual property. Firms engage in dynamic, Schumpeterian competition for the market, through sequential winner-take-all races to produce drastic innovations, rather than through static price/output competition in the market....

We explore how financial constraints distort the entry decisions among otherwise productive entrepreneurs and limit growth of promising young firms. A model of liquidity-constrained entrepreneurs suggests that the easing of credit constraints can induce more entry of firms with greater long-run...

We study the direct and indirect effects of randomized entry. In partnership with the two largest service providers in Ghana, we implement a three-step design that randomizes the entry of new financial mobile money vendors, who also sell non-financial goods/services, across local markets. This...

Adverse selection is a classic market failure known to limit or "unravel"' trade in high-quality insurance and many other economic settings. While the standard theory emphasizes quality distortions, we argue that selection has another big-picture implication: it unravels competition among...

We investigate the influence of the growing trend of work-from-home (WFH) on new business formation, with a particular focus on the period surrounding the COVID-19 pandemic. At baseline, local new business entry is positively associated with the proportion of occupations amenable to telework in...

"Using a comprehensive database of firms in Western and Eastern Europe, we study how the business environment in a country drives the creation of new firms. Our focus is on regulations governing entry. We find entry regulations hamper entry, especially in industries that naturally should have...

Sunk costs play a central role in antitrust economics, but are often misunderstood and mismeasured. I will try to clarify some of the conceptual and empirical issues related to sunk costs, and explain their implications for antitrust analysis. I will be particularly concerned with the role of...

Efforts to strengthen the global patent system for pharmaceuticals continue to be controversial, and what will likely be a similarly fraught international debate over price controls has begun. The outcome of international negotiations and the resulting policy decisions made by each country will...