You'll need Excel or a compatible spreadsheet to see the data. The link on the IRS website is http://www.irs.ustreas.gov/pub/irs-soi/00in01rt.xls. If you don't have Excel, you might be able to download a free Excel viewer program online.

The most recent data is from the year 2000, although the spreadsheet covers the period from 1986 through 2000. In case you can't get to the data, here's a summary. First of all, the original poster said that the "bottom 50% of taxpayers only pay 3.6%" of taxes." That's different from your misstatement that "the rich pay 96.4% of taxes" unless you think anyone who had an adjusted gross income of over $27,682 in 2000 as being "rich". That was the dividing point between the top and bottom 50% of wage earners (cell G42). Here are the breakouts by percentage (cells C42 through G42) for the year 2000:

Top 1%: >= $313,469
Top 5%: >= $128,336
Top 10%: >= $92,144
Top 25%: >= $55,225
Top 50%: >= $27,682
Bottom 50%: < $27,682

Scroll on down in the spreadsheet to cells C149 through G149 and you'll see that in the year 2000:

Top 1% paid 37.42% of all income tax
Top 5% paid 56.47% of all income tax
Top 10% paid 67.33% of all income tax
Top 25% paid 84.01% of all income tax
Top 50% paid 96.09% of all income tax
Top 50% paid 3.91% of all income tax

Lest you think those percentages are in line with their income, check out cells C133 through G133. You'll see that in the year 2000:

Top 1% made 20.81% of total income
Top 5% made 35.30% of total income
Top 10% made 46.01% of total income
Top 25% made 67.15% of total income
Top 50% made 87.01% of total income
Bottom 50% made 12.99% of total income

Pretty well puts the lie to the old line "the rich don't pay taxes."