In 2006, the Tax Foundation said that 41% of all americans are outside the tax system meaning they dont pay taxes or get refunds equal to what was deducted !!!!!

This was what they concluded in this report....

"Conclusion
These findings raise serious questions about the future of the U.S. income tax system, and the possibility of base-broadening tax reform when the majority of the federal tax burden is borne by a shrinking pool of taxpayers. As Congress considers tax reform proposals during the coming year, this is an issue lawmakers should begin to debate."

http://www.taxfoundation.org/news/show/1410.html

Also as of 2006, the top 10% income earners pay 70.79% of the TOTAL income tax.