"Thomas Piketty and Emmanuel Saez wrote in their work "Income Inequality in the United States,1913–1998" that "top income and wages shares(in the United States) display a U-shaped pattern over the century" and "that the large shocks that capital owners experienced during the Great Depression and World War II have had a permanent effect on top capital incomes...that steep progressive income and estate taxation may have prevented large fortunes from recovery form the shocks."