The fall of labor's share of GDP in the United States and many other countries in recent decades is well documented but its causes remain uncertain. Existing empirical assessments of trends in labor's share typically have relied on industry or macro data, obscuring heterogeneity among firms. In...

The recent fall of labor's share of GDP in numerous countries is well-documented, but its causes are poorly understood. We sketch a "superstar firm" model where industries are increasingly characterized by "winner take most" competition, leading a small number of highly profitable (and low labor...

This paper explores how different margins of market share are related to markups. Using merged microdata on producers and consumers, we document that a firm's market share is mainly related to its number of customers, while its price-cost markup is associated only with its average sales per...

We examine the interplay between market structure and the form that commodity taxation should take in a general equilibrium model in which firms produce differentiated products and so are able to exert market power. Our analysis takes account of two important recent developments that affect...

National industrial concentration in the U.S. has risen sharply since the early 1980s, but there remains dispute over whether local geographic concentration has followed a similar trend. Using near population data from the Economic Censuses, we confirm and extend existing evidence on national...

Concentration is a single summary statistic driven by two opposing forces: the number of firms in a market and the evenness of their market shares. This paper introduces a generalized measure of concentration that allows researchers to vary the relative importance of each force. Using the...

Using an aggregative games approach, we analyze horizontal mergers in a model of multiproduct-firm price competition with nested CES or nested logit demands. We show that the Herfindahl index provides an adequate measure of the welfare distortions introduced by market power, and that the induced...

This study provides a new theoretical result that low interest rates encourage market concentration by raising industry leaders' incentive to gain a strategic advantage over followers, and this effect strengthens as the interest rate approaches zero. The model provides a unified explanation for...