Check out the chart in this article at the Huffington Post:

http://www.huffingtonpost.com/daron-acemoglu/us-inequality_b_1338118.html

A couple of excerpts:

<< Occupy Wall Street (OWS) brought the increased inequality in the U.S. to the headlines, where it deserves to be. Almost a quarter of total U.S. national income now accrues to the richest 1 percent of the population, a figure that was barely above 10 percent 40 years ago. Other countries, most notably the U.K., have also witnessed growing inequality, but none competes with the U.S. in the surge in inequality. Is it unfair and unjust for so few to become so much richer than the rest? >>

[snip]

<< So here is the concern: economic inequality will lead to greater political inequality, and those who are further empowered politically will use this to gain a greater economic advantage by stacking the cards in their favor and increasing economic inequality yet further -- a quintessential vicious circle. >>

It will undoubtedly be an important issue in this year's elections.