Wage inequality has risen in many countries over recent decades. At the same time, production has become increasingly concentrated in "superstar" firms. In this paper, we show that these two phenomena are linked. Theoretically, we show that shocks that increase concentration, such as an increase...

We propose uncertainty shocks as a new shock that drives business cycles. First, we demonstrate that microeconomic uncertainty is robustly countercyclical, rising sharply during recessions, particularly during the Great Recession of 2007-2009. Second, we quantify the impact of time-varying...

We propose uncertainty shocks as a new shock that drives business cycles. First, we demonstrate that microeconomic uncertainty is robustly countercyclical, rising sharply during recessions, particularly during the Great Recession of 2007-2009. Second, we quantify the impact of timevarying...