For those wondering how we've been doing relative to that 19.5% of GDP, here's a graph: http://carriedaway.blogs.com/carried_away/2005/04/us_governm...
We probably couldn't lower taxes for a while after spending less than 19.5% of GDP so we could actually pay down the national debt, but I like your plan.
US GDP growth hasn't changed, even as this highest marginal tax rate moved by a factor of 3. It was actually highest in the 60s and 70s, when the top rate was still in the 70% range.
GDP and total revenues are just too big to be affected by the tax rate of a single group, even, the most wealthy.
What this budget shows us is that total gov’t spending must never be over 19.5% of GDP. That’s the only solution. Then, we can start lowering taxes and see if revenues stay up.