Piketty's correction (WSJ):
Though his formula helps explain extreme and persistent wealth inequality before World War I, Mr. Piketty maintains, it doesn’t say much about the past 100 years. “I do not view r>g as the only or even the primary tool for considering changes in income and wealth in the 20th century,” he writes, “or for forecasting the path of inequality in the 21st century.”More here (WSJ): "Why Thomas Piketty’s Revisions Don’t Fix His Book."
Instead, Mr. Piketty argues in his new paper that political shocks, institutional changes and economic development played a major role in inequality in the past and will likely do so in the future.
When he narrows his focus to what he calls “labor income inequality”—the difference in compensation between front-line workers and CEOs—Mr. Piketty consigns his famous formula to irrelevance. “In addition, I certainly do not believe that r>g is a useful tool for the discussion of rising inequality of labor income: other mechanisms and policies are much more relevant here, e.g. supply and demand of skills and education.” He correctly distinguishes between income and wealth, and he takes a long historic perspective: “Wealth inequality is currently much less extreme than a century ago.”