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 ...

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."

The great irony is that, in the name of reducing inequality, some of our politicians want to raise taxes and other government obstacles to the kind of risk-taking and hard work that allow Americans to climb the income ladder so rapidly. As the Treasury data show, we shouldn't worry about inequality. We should worry about the people who use inequality as a political club to promote policies that reduce opportunity.