From the Center on Budget and Policy Priorities:
The new [Congressional Budget Office] data document [shows] that income inequality continued to widen in 2004. The average after-tax income of the richest one percent of households rose from $722,000 in 2003 to $868,000 in 2004, after adjusting for inflation, a one-year increase of nearly $146,000, or 20 percent. This increase was the largest increase in 15 years, measured both in percentage terms and in real dollars.
In contrast, the income of the middle fifth of the population rose $1,700, or 3.6 percent, to $48,400 in 2004. The income of the bottom fifth rose a scant $200 (or 1.4 percent) to $14,700.