There is extensive literature on this topic, and discussions are found in Fields (1995), Li et al. ( Most recently, Piketty (2014) shows that inequality in both the United States and in Europe may have actually followed a U-shaped curve in the twentieth century - contrary to what the Kuznets curve would suggest. Some of the progressive measures introduced in the post-war period were rolled back in the 1970s and 1980s (Piketty 2015).