<P> Most of the growth in income inequality has been between the middle class and top earners , with the disparity widening the further one goes up in the income distribution . The bottom 50 % earned 20 % of the nation 's pre-tax income in 1979 ; this fell steadily to 14 % by 2007 and 13 % by 2014 . Income for the middle 40 % group , a proxy for the middle class , fell from 45 % in 1979 to 41 % in both 2007 and 2014 . </P>
roughly 40 to 45 percent of the u.s. population falls within the largest social class which is the
middle class