This paper presents new homogeneous series on top shares of income and wages in the United States from 1913 to 1998 using individual tax return data. The data shows a U-shaped pattern in top income and wage shares over the century. The "technical change" view of inequality dynamics cannot fully explain the observed facts. Large shocks to capital owners during the Great Depression and World War II had a lasting effect, with top capital incomes still lower in the late 1990s than before World War I. A plausible explanation is that progressive taxation reduced wealth accumulation at the top, preventing large fortunes from recovering fully. Wage inequality data shows that top wage shares were flat before WWII and dropped sharply during the war. They have since recovered and are now higher than before WWII. The paper emphasizes the role of social norms in explaining wage share patterns. The data shows that top capital incomes were severely hit by major shocks during 1914-1945, with the Great Depression and wars having a significant impact. Top wage shares dropped sharply during WWII but have since recovered. The paper argues that both the downturn and upturn in top wage shares are too sudden to be explained by technical change alone, and emphasizes the role of changing social norms. The paper also discusses the role of progressive taxation in reducing capital income concentration and the impact of tax policies on wealth inequality. The findings suggest that the decline in top capital incomes is largely due to high taxation, not technological change. The paper concludes that the reduction in capital income concentration is mainly due to the shocks of the inter-war period and wars, and that progressive taxation has played a key role in this. The paper also shows that wage inequality has increased substantially in the last three decades and is now as high as in the inter-war period. The paper argues that the US may experience again levels of wealth concentration similar to those of the beginning of the century if tax progressivity declines and the estate tax is repealed.This paper presents new homogeneous series on top shares of income and wages in the United States from 1913 to 1998 using individual tax return data. The data shows a U-shaped pattern in top income and wage shares over the century. The "technical change" view of inequality dynamics cannot fully explain the observed facts. Large shocks to capital owners during the Great Depression and World War II had a lasting effect, with top capital incomes still lower in the late 1990s than before World War I. A plausible explanation is that progressive taxation reduced wealth accumulation at the top, preventing large fortunes from recovering fully. Wage inequality data shows that top wage shares were flat before WWII and dropped sharply during the war. They have since recovered and are now higher than before WWII. The paper emphasizes the role of social norms in explaining wage share patterns. The data shows that top capital incomes were severely hit by major shocks during 1914-1945, with the Great Depression and wars having a significant impact. Top wage shares dropped sharply during WWII but have since recovered. The paper argues that both the downturn and upturn in top wage shares are too sudden to be explained by technical change alone, and emphasizes the role of changing social norms. The paper also discusses the role of progressive taxation in reducing capital income concentration and the impact of tax policies on wealth inequality. The findings suggest that the decline in top capital incomes is largely due to high taxation, not technological change. The paper concludes that the reduction in capital income concentration is mainly due to the shocks of the inter-war period and wars, and that progressive taxation has played a key role in this. The paper also shows that wage inequality has increased substantially in the last three decades and is now as high as in the inter-war period. The paper argues that the US may experience again levels of wealth concentration similar to those of the beginning of the century if tax progressivity declines and the estate tax is repealed.