Studies by the Department of the Treasury of actual US tax returns demonstrate substantial income mobility in the US (1987-1996, 1996-2005). For instance, among those in the lowest income quintile in 1987, 60 percent of them experienced at least a fifty percent increase in their income by 1996 and median income increased 80.6 percent. Another way to look at this is that 61 percent of those in the lowest income quintile in 1987 were in a higher income quintile by 1996. Income mobility maintained approximately the same pace between 1996-2005. For instance, 64 percent among those in the lowest income quintile in 1987 experienced at least a fifty percent increase in their income by 2005, and median income increased 90.5 percent. Moreover, the second, third, and fourth income quintiles experienced 35, 23, and 17 percent median income growth respectively between 1996 and 2005. US Treasury data also show a great deal of volatility even for top income groups. For instance, incomes were cut in half among 59 percent for those in the top .01 percent between 1996 and 2005.
A great deal of income mobility coupled with increasing inequality suggests that people are traveling a further distance up the income ladder. In sum, it’s more meaningful to climb the economic ladder in the US than say, in Norway, where incomes are more equal, but the ladder doesn’t take you as far. Certainly, the 2008 financial crisis and pursuant sluggish economy have slowed down economic mobility, making income gaps more obvious. This may explain why in the
September Reason-Rupe poll we found a sizable 37 percent of Americans who fear their children will have fewer opportunities to get ahead. At the same time 56 percent are optimistic their children will have more opportunities (27 percent) or the same opportunities (29 percent) to get ahead.
http://reason.com/poll/2012/11/02/despite-the-presidential-election-americ