I dont' have time to wade through this, but maybe data can be found here.
http://www.irs.gov/taxstats/indtaxst...=96981,00.html
The table shown above (if accurate) is somewhat misleading. It shows only a slice of the tax picture (federal income taxes)--no state, property, sales, Social Security, or tax-exempt income shown. No capital accruement shown. It also doesn't show us anything about a taxpayer's ability to pay, for example, what portion of his income goes to taxes. A progressive tax system is designed so that those who can pay more, do. I think that's fair.