The income share of the super-rich in the United States has grown rapidly since the early 1980s after a period of postwar stability. What factors drove this change? In this study, we investigate the institutional, policy, and economic shifts that may explain rising income concentration. We use single-equation error correction models to estimate the long- and short-run effects of politics, policy, and economic factors on pretax top income shares between 1949 and 2008. We find that the rise of the super-rich is the result of rightward-shifts in Congress, the decline of labor unions, lower tax rates on high incomes, increased trade openness, and asset bubbles in stock and real estate markets.