The Congressional Research Service recently released a report about the distribution of income between 1996 and 2006.

Inflation-adjusted average after-tax income grew by 25% between 1996 and 2006 (the last year for which individual income tax data is publicly available). This average increase, however, obscures a great deal of variation. The poorest 20% of tax filers experienced a 6% reduction in income while the top 0.1% of tax filers saw their income almost double. Tax filers in the middle of the income distribution experienced about a 10% increase in income. Also during this period, the proportion of income from capital increased for the top 0.1% from 64% to 70%.