Although the US continues to have one of the highest levels of income disparities in the developed world, the growth in income disparity has been about as great or greater in other countries, including those with substantially different economic and social systems, including Israel, New Zealand, Germany, France, Finland and Sweden.
So, to the extent this is a problem in the U.S., we are not alone in it getting worse.
The only country that showed a decline in income disparity was Greece, perhaps due to their financial system cratering which, I suppose, is one way to solve the problem.
The OECD chart below gives the relevant data - increases are shown by the distance between the top of the blue lines and the red diamonds.
See the OECD Report at www.oecd.org/document/40/0,3746,en_21571361_44315115_49166760_1_1_1_1,00.html