I provide evidence that investor size matters in the market for short-term securities. Between January 2011 and November 2020, the largest asset management families obtained significantly higher promised returns from their money market securities than smaller families. Furthermore, I show that...

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...