Brad Delong: Owen Zidar sends us to Facundo Alvaredo, Anthony B. Atkinson, Thomas Piketty, and Emmanuel Saez: The Top 1 Percent in International and Historical Perspective: "The top 1 percent income share has more than doubled in the United States over the last thirty years… other English speaking countries have also experienced sharp increases… [but] many high-income countries such as Japan, France, or Germany have seen much less increase…. Hence, the explanation cannot rely solely on forces common to advanced countries, such as the impact of new technologies and globalization on the supply and demand for skills. Moreover, the explanations have to accommodate the falls in top income shares earlier in the twentieth century…. We highlight four…. The first is the impact of tax policy…. Top tax rates have moved in the opposite direction from top income shares…. The second factor is indeed a richer view of the labor market, where we contrast the standard supply-side model with one where pay is determined by bargaining…. The third factor is capital income…. The fourth, little investigated, element is the correlation between earned income and capital income, which has substantially increased in recent decades in the United States."