21 Percent of US Working Age Adults Are In Top 2 Percent By Income For At Least One Year: Percentage Doubled Since 1979

From TIME, Business & Money, "Rising Riches: 1 in 5 in U.S. Reaches Affluence" by Hope Yen, Associated Press:

Fully 20 percent of U.S. adults become rich for parts of their lives, wielding outsize influence on America’s economy and politics. This little-known group may pose the biggest barrier to reducing the nation’s income inequality.***Made up largely of older professionals, working married couples and more educated singles, the new rich are those with household income of $250,000 or more at some point during their working lives. That puts them, if sometimes temporarily, in the top 2 percent of earners.

Even outside periods of unusual wealth, members of this group generally hover in the $100,000-plus income range, keeping them in the top 20 percent of earners.***In a country where poverty is at a record high, today’s new rich are notable for their sense of economic fragility. They’ve reached the top 2 percent, only to fall below it, in many cases. That makes them much more fiscally conservative than other Americans, polling suggests, and less likely to support public programs, such as food stamps or early public education, to help the disadvantaged.***New research suggests that affluent Americans are more numerous than government data depict, encompassing 21 percent of working-age adults for at least a year by the time they turn 60. That proportion has more than doubled since 1979.