The income of the richest 1 percent in the U.S. soared 275 percent from 1979 to 2007, but the bottom 20 percent grew by just 18 percent, new government data shows.

The Congressional Budget Office (CBO) released a study this week that compared real after-tax household income between 1979 and 2007, which were both after recessions and had similar overall economic activity.

While the income of the richest 1 percent nearly tripled, increases were smaller down the economic ladder. After the 1 percent, income for the next highest 20 percent grew by 65 percent, much faster than it did for the remaining 80 percent of the population but still lagging well behind the top percentile.
The changes illustrate how the better off have captured the bulk of income gains over the past three decades. The top quintile has seen its share of income rise while the other four quintiles have suffered declines in their shares, according to John Bowler, director of country risk service with the Economist Intelligence Unit.

The report states that without the growth of the top percentile, income inequality still would have increased, "but not by nearly as much." The study was prepared at the request of Sens. Max Baucus, D-Mont., and Charles Grassley, R-Iowa.