The story of '2 America's' as told by John Edwards

The Treasury study examined a huge sample of 96,700 income tax returns from 1996 and 2005 for Americans over the age of 25. The study tracks what happened to these tax filers over this 10-year period. One of the notable, and reassuring, findings is that nearly 58% of filers who were in the poorest income group in 1996 had moved into a higher income category by 2005. Nearly 25% jumped into the middle or upper-middle income groups, and 5.3% made it all the way to the highest quintile.
Of those in the second lowest income quintile, nearly 50% moved into the middle quintile or higher, and only 17% moved down. This is a stunning show of upward mobility, meaning that more than half of all lower-income Americans in 1996 had moved up the income scale in only 10 years.

Also encouraging is the fact that the after-inflation median income of all tax filers increased by an impressive 24% over the same period. Two of every three workers had a real income gain. This is even more impressive when you consider that "median" income and wage numbers are often skewed downward because the U.S. has had a huge influx of young workers and immigrants in the last 20 years. They start their work years with low wages, dragging down the averages.

Those who start at the bottom but hold full-time jobs nonetheless enjoyed steady income gains. The Treasury study found that those tax filers who were in the poorest income quintile in 1996 saw a near doubling of their incomes (90.5%) over the subsequent decade. Those in the highest quintile, on the other hand, saw only modest income gains (10%). The nearby table tells the story, which is that the poorer an individual or household was in 1996 the greater the percentage income gain after 10 years.

Only one income group experienced an absolute decline in real income--the richest 1% in 1996. Those households lost 25.8% of their income. Moreover, more than half (57.4%) of the richest 1% in 1996 had dropped to a lower income group by 2005. Some of these people might have been "rich" merely for one year, or perhaps for several, as they hit their peak earning years or had some capital gains windfall. Others may simply have not been able to keep up with new entrepreneurs and wealth creators.

The key point is that the study shows that income mobility in the U.S. works down as well as up--another sign that opportunity and merit continue to drive American success, not accidents of birth. The "rich" are not the same people over time.

The study is also valuable because it shows that income mobility remains little changed from what similar studies found in the 1970s and 1980s. Some journalists and academics have cited selective evidence to claim that income mobility has declined in recent years.

But the 58% of lowest-income earners who moved to a higher income quintile in this study is roughly comparable to the percentages that did so in several similar studies going back to the late 1960s. "The basic finding of this analysis," says the Treasury report, "is that relative income mobility is approximately the same in the last 10 years as it was in the previous decade."