<P> U.S. income inequality has grown significantly since the early 1970s, after several decades of stability, and has been the subject of study of many scholars and institutions . The U.S. consistently exhibits higher rates of income inequality than most developed nations due to the nation's enhanced support of free market capitalism and less progressive spending on social services . </P> <P> The top 1% of households received approximately 20% of the pre-tax income in 2013, versus approximately 10% from 1950 to 1980 . The top 1% is not homogeneous, with the very top income households pulling away from others in the top 1% . For example, the top 0.1% of households received approximately 10% of the pre-tax income in 2013, versus approximately 3--4% between 1951--1981 . According to IRS data, adjusted gross income (AGI) of approximately $430,000 was required to be in the top 1% in 2013 . </P> <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> <P> To put this change into perspective, if the US had the same income distribution it had in 1979, each family in the bottom 80% of the income distribution would have had $11,000 more per year in income on average in 2012, or $916 per month . This figure would be $7,100 per year for the bottom 99% of families comparing 1979 and 2012, or about $600 / month . </P>

Roughly 40 to 45 percent of the u.s. population falls within the largest social class which is the