We combine a structural model with cross-sectional micro data to identify the causes and consequences of rising concentration in the US economy. Using asset prices and industry data, we estimate realized and anticipated shocks that drive entry and concentration. We validate our approach by...

We measure the evolution of dominant firms in the U.S. economy since 1960, and globally since 1990. Contrary to common wisdom, dominant firms have not become larger, have not become more productive, and their contribution to aggregate productivity growth has fallen by more than one third since 2000