You can go to the IRS web site. The data is all there.
This is from 2002:
Income Group —- Tax Share
Top 1 percent —- 33.7 percent
Top 5 percent —- 53.8 percent
Top 10 percent —- 65.7 percent
Top 25 percent —- 83.9 percent
Top 50 percent —- 96.5 percent
