During the last couple of decades, there has been an increase in income inequality in the United States.

Which of the following is a reason income inequality in the United States has increased?

There has been a great increase in efficiency of government antipoverty programs.

There has been a significant drop in the number of single-parent families.

There has been an increase in the number of markets that are characterized by a few people at the top with very high earnings.

Marginal tax rates have increased significantly since the 1970s.