How has income distribution changed in the U.S. in the last 40 years?

 How has income distribution changed in the U.S. in the last 40 years? A. Middle-class Americans have seen their incomes grow much more quickly than wealthy Americans, B. Wealthy Americans and middle-class Americans have seen their incomes grow at about the same rate, or C. Wealthy Americans have seen their incomes grow much more quickly than middle-class Americans.