Two to one third

"Firm statistics from the University of California, Berkeley, have proved that, in the United States, more than 80 percent of the total increase in income in the quarter-century to 2005 was enthusiastically sequestered by just the top one per cent of the population. That was the year fortunes of Bill Gates and Warren Buffett ($89 billion) nearly eclipsed the combined wealth of the bottom 120 million Americans ($95 billion)" Urgent pleas: help support Australia's battling billionaires, but Nicholas Stuart, in Canberra Times, 29 Jan 2011, Opinion, p.25.

No comment required really, other than that 120 million is about one third of all of the population of the US.

And more from later that day:

"The Economic Policy Institute reports that the top one per cent of households in the US holds 34.3 per cent of private wealth, more that the bottom 90 per cent combined" Teh hole in America's middle, by Mark Engler, in New Internationalist, no. 439, Jan/Feb 2011, p.22.