Digression- 2007 figures-
138 million taxpayers in U. S., one-third of whom pay zero tax.
In other words, about 90 million pay federal taxes.

The top 1% of income earners pay 36.9% of federal taxes. The top 5% pay 57% of taxes (they have about 57% of the wealth).
The bottom 50% pay 3.3% of taxes.
For wage earners, the payroll tax system (FICA) imposes a 12.4% Social Security tax on wages up to $97,500 and a 2% Medicare tax, thus acts regressively.
Three-fourths of U. S. taxpayers pay more in payroll taxes than income taxes.

The Tax Foundation has stated that the burden of the corporate income tax (a 15%-39% tax) falls on customers and workers of the corporations, who are often not rich.

Jus a few figures for my own information. Most from Wikipedia, "Taxation in the United States."

(Add state and local taxes. Congressionally enacted tax credits skew the system. Etc.)