The federal income tax code is now so mangled that we can probably increase federal revenues with a 0% income tax rate for a majority of Americans.
Long before President Barack Obama took office, the bottom 40% of income earners paid no federal income taxes. Because of refundable income tax credits like the Earned Income Tax Credit (EITC), in 2006 these bottom 40% as a group actually received net payments equal to 3.6% of total income tax revenues, according to the latest Congressional Budget Office data. The actual middle class, the middle 20% of income earners, pay only 4.4% of total federal income tax revenues. That means the bottom 60% together pay less than 1% of income tax revenues.