 In March 2018, the CBO reported that the ACA had reduced income inequality in 2014, saying that the law led the lowest and second quintiles (the bottom 40%) to receive an average of an additional $690 and $560 respectively while causing households in the top 1% to pay an additional $21,000 due mostly to the net investment income tax and the additional Medicare tax.The law placed relatively little burden on households in the top quintile (top 20%) outside of the top 1%.Princeton economics professor, Nobel laureate, and John Bates Clarke Award winner Paul Krugman argues that politics not economic conditions have made income inequality in the United States "unique" and to a degree that "other advanced countries have not seen."