Historical Tax Rates by Quintiles

Lowest quintile: 4.3 percent
Second quintile: 9.9 percent
Middle quintile: 14.2 percent
Fourth quintile: 17.4 percent
Percentiles 81-90: 20.3 percent
Percentiles 91-95: 22.4 percent
Percentiles 96-99: 25.7 percent
Percentiles 99.0-99.5: 29.7 percent
Percentiles 99.5-99.9: 31.2 percent
Percentiles 99.9-99.99: 32.1 percentTop 0.01
Percentile: 31.5 percent

N.B.: These figures include all federal taxes, not just income taxes.

source (HT: Greg Mankiw)