Just how much do the richest 5% in the US pay in taxes?

[Unclebananahead]

In his article, "The Politics Of Avoidance," Newsweek columnist Robert J. Samuelson writes, "Liberals would solve the budget problem by taxing the rich and cutting defense. Think Again. The richest 5 percent already pay about 45 percent of federal taxes; they may pay more but not enough to balance the budget"

My question for my fellow RevLefters is this: just how much do the richest 5% in the US actually pay in taxes? How accurate (or perhaps rather, inaccurate) are Mr. Samuelson's figures?

[WeAreReborn]

" And the top 1% of income earners, who average over $1 million a year, actually pay a smaller percentage of their incomes to taxes than the 9% just below them. These findings are discussed in detail near the end of this document."
What I found from a paper from UCSC. I apologize that it doesn't directly answer your question but does show a hierarchy in terms of wealth and tax amount paid.
http://sociology.ucsc.edu/whorulesamerica/power/wealth.html