Inequality in models with a competition for market shares

This paper develops a framework to systematically study how changes in market conditions affect the equilibrium inequality between heterogeneous agents. By stating our setting as a "competition for market shares", we can derive inequality predictions for vastly different competition models. This approach allows us to identify a common structure, e.g., in monopolistic competition, perfect competition, or competition for prizes, that explains why these models deliver similar inequality predictions. We apply our results to problems from trade, competition theory, consumption inequality, political economics and marketing, and relate some of the predicted inequality patterns to empirical evidence.