The latest data show that a big portion of the federal income tax burden is shoul*dered by a small group of the very richest Americans. The wealthiest 1 percent of the population earn 19 per*cent of the income but pay 37 percent of the income tax. The top 10 percent pay 68 percent of the tab. Meanwhile, the bottom 50 percent—those below the median income level—now earn 13 percent of the income but pay just 3 percent of the taxes. These are proportions of the income tax alone and don’t include payroll taxes for Social Security and Medicare.
http://www.american.com/archive/2007...pays-the-taxes