US already moving toward a flat tax

Billionaires are paying not much more taxes, proportionately, than those Americans who are merely prosperous.
It's a sign that, even without the formal adoption of a so-called "flat tax," America's tax system is getting flatter.
...If the Bush tax cuts are made permanent by Congress, by 2010 billionaires and millionaires will be paying a smaller percentage of their income in federal taxes than those in the upper middle class, according to a calculation by Brian Roach, an economist at Tufts University, in Medford, Mass.
In his second term, Bush has identified further tax reform as a top goal. This could include a push for a flat tax, one in which all income groups are asked to pay the same rate.