That's hard, irateplatypus, but here's what I get from the IRS. (2002) The top 10% is anybody making over $92,754 AGI. Given that there were 130,904,889 returns filed, that's 13,090,489 people. Estimating income is interesting, but the top 1% is $292,913, so if I average those and call that the average for the top 10%, I think that's reasonable. (92,754+292,913)/2 = 192,834. The problem now becomes how many of those returns are single and how many are married?
Single people making that amount are taxed roughly $51,000.
Head of household is just over $48,000.
Married(or qualified widowed) is not quite $45,000.
And Married filing separately is the highest, almost $55,000.
So let me assume worst case, and every single person in the top ten percent is married filing separately, and is taxed an average of $55K. The IRS collected $1,037,734,000,000. Just over a trillion dollars. And the top ten percent (just over 13 million people) are paying 55K a pop. That's 715 billion dollars, or 71.5%.
So not 90%, even with the allowances made toward the Limbaugh numbers.
I used this form:
http://www.irs.gov/pub/irs-pdf/f1040es.pdf to estimate tax burden.