Check out this chart of taxes and jobs in Presidential administrations back to the Great Depression. The middle number is the average tax % for the top tier. The third number is the average annual job growth.
If you buy that job creation is tied to the taxes on the wealthy, then from these figures the ideal top tax rate would be somewhere in the area of 75% ... certainly in the 70 to 89% range. According to the notion that job creation is tied to taxes on the wealthy, clearly we need to at least double the taxes on the top bracket in order to ramp up job creation.
[I don't necessarily believe that notion, but even without that it still looks like we've dropped taxes on the wealthy too low.]
Figures from http://en.wikipedia.org/wiki/Jobs_created_during_U.S._presidential_terms and http://www.ntu.org/tax-basics/history-of-federal-individual-1.html