This chart was posted yesterday at Ace of Spades (it's from the Wall Street Journal):
In case you don't know the line, Willie Sutton was a notorious bank robber, and when a reporter asked him, "Why do you rob banks?" he answered, simply, "Because that's where the money is." I think the reporter meant to ask why do you rob at all, whereas Sutton took the question to mean why do you rob banks. Sutton just assumed the "robbing" part and focused on the choice of target.
The Democrats have a similar mentality. If you put them under truth serum and ask "Why are you creating the circumstances under which we will have no choice but to heavily tax the middle class?" they'll answer "Because that's where the money is." Like Willie Sutton, they assume the "rob" part is obvious; they're just focusing on the target for the heist.
The following chart is not of taxes paid by different income level cohorts -- it's a chart of the total income available to be taxed within each grouping.
Link
But, but...that's the goal of communism. Simply stated, in order for class warfare to work, you must eliminate the middle class pitting wealth against poverty, that's why it worked in Russia initially, peasants against the aristocracy, unitl the peasants realzed that they traded one tyrant for another.