Which of the Following Contributed to the Increase in Income

Multiple Choice

Which of the following contributed to the increase in income inequality among families in the United States during the 1980s and 1990s?

A) an increase in the highest marginal tax rates that forced high income earners to work more in order to maintain their income
B) an increase in the proportion of both single-parent and dual-earner families
C) a decrease in the size of the earnings differential between college graduates and high school graduates
D) all of the above