We present a new model of competition between digital media platforms with targeted advertising. The model adds new insights around how user heterogeneity and overlap, along with user and advertiser substitution patterns, determine equilibrium ad load. We apply the model to evaluate the proposed...

This paper empirically analyzes the effects of mergers between complementary firms on competition and pricing. As these non-horizontal mergers have become more common, there is increasing interest in evaluating both potential efficiencies such as eliminating double marginalization and potential...

This paper studies whether common leadership, defined as two firms sharing executives or board directors, contributes to collusion. Using an explicit measure of labor market collusion from unsealed court evidence, we find that the probability of collusion between two firms increases by 12...

While numerous papers document the effects of mergers on cost and quality, the effects of hospital mergers on access to care are less certain. Merging hospitals may limit access by closing one of the affected hospitals or eliminating individual service lines. However, hospital systems may have...

We develop a simple model to explain why a powerful importer country like the United States may provide political support for international collusive agreements concerning certain commodities (e.g., coffee). This behavior raises questions due to the fact that an importer country should have...

We propose an equilibrium theory of data-driven antitrust oversight in which regulators launch investigations on the basis of suspicious bidding patterns and cartels can adapt to the statistical screens used by regulators. We emphasize the use of asymptotically safe tests, i.e. tests that are...

We examine merging firms' additions and removals of products for a sample of 66 mergers across a wide variety of consumer packaged goods markets. We find that mergers lead to a net reduction in the number of products offered by merging firms. Merging firms tend to both drop and add products at...

Between 2000 and 2020, the share of US hospital bed capacity under multi-unit firms (systems) increased from 58% to 81% - a rapid corporatization of a sector with $1.3 trillion in annual spend. However, little is known about how system ownership affects hospital profitability and quality. We...

This paper examines the evolving structure and competition dynamics of the rapidly growing market for foundation models, with a focus on large language models (LLMs). We describe the technological characteristics that shape the AI industry and have given rise to fierce competition among the...

We hand-collect and standardize information describing all 3,055 antitrust lawsuits brought by the Department of Justice (DOJ) between 1971 and 2018. Using restricted establishment-level microdata from the U.S. Census, we compare the economic outcomes of a non-tradable industry in states...