There are two main types of mobility, absolute and relative.[1] Absolute upward mobility involves widespread economic growth which benefits everyone[1]. Relative mobility is specific to individuals and occurs without relation to the economy as a whole[1]. Both absolute and relative income mobility has been large and upward in the past ten years for those starting with below-average incomes; 80 percent of taxpayers had incomes in quintiles as high or higher in 2005 than they did in 1996, and 45 percent of taxpayers not in the highest income quintile moved up at least one quintile[2].
There has been a great disparity of income growth between 1979 and 2004 in the United States. The real, after-tax income of the top 1% earners has grown by 176% percent during that time, compared to a 69% rise for the top 20%, and an increase of 9% for the lowest 20%[1]. Increasing income inequality, however, does not necessarily imply decreasing mobility. Median family income has risen 29% and mean family income has risen 43%, compared to the income of the previous generation for people that were children in 1968[3]. Most of this growth in total family income can be attributed to the increasing number of women who work since male earnings have stayed relatively stable throughout this time[3]. Two thirds of those who were children in 1968 reported more income than their parents, but only half of them exceeded their parents economic standing by moving up one or more quintiles[3]. Although one third of the nation is moving up quintiles, another third is downwardly mobile — experiencing a decrease in income and economic standing compared to their parents[3].
Moving between quintiles is more frequent in the middle quintiles (2-4) than in the lowest and highest quintiles. Of those in one of the quintiles 2-4 in 1996, approximately 35% stayed in the same quintile; and approximately 22% went up one quintile or down one quintile (moves of more than one quintile are rarer). However, 42% of children born in the bottom quintile are most likely to stay there, and another 42% move up to the second and middle quintile[3]. On the opposite end of the spectrum, 39% of those who were born into the top quintile as children in 1968 are likely to stay there, and 23% end up in the fourth quintile[3]. Children previously from lower-income families had only a 1% chance of having an income that ranks in the top 5%[4]. On the other hand, the children of wealthy families have a 22% chance of reaching the top 5%[4].