We examine characteristics of the 400 wealthiest individuals in the United States over the past three decades as tabulated by Forbes Magazine, and analyze which theories of increasing inequality are most consistent with these data. The people of the Forbes 400 in recent years did not grow up as advantaged as in decades past. They are more likely to have started their businesses and to have grown up upper-middle class, not wealthy. Today's Forbes 400 were able to access education while young, and apply their skills to the most scalable industries: technology, finance, and mass retail. Most of the change occurred by 2001.

We examine the impact of short selling by conducting a randomized stock lending experiment. Working with a large, anonymous money manager, we create an exogenous and sizeable shock to the supply of lendable shares by taking high loan fee stocks in the manager's portfolio and randomly making available and withholding stocks from the lending market. The experiment ran in two independent phases: the first, from September 5 to 18, 2008, with over $580 million of securities lent, and the second, from June 5 to September 30, 2009, with over $250 million of securities lent. While the supply shocks significantly reduce market lending fees and raise quantities, we find no evidence that returns, volatility, skewness, or bid–ask spreads are affected. The results provide novel evidence on the impact of shorting supply and do not indicate any adverse effects on stock prices from securities lending.