During 2006, Tax Foundation economists estimate that roughly 43.4 million tax returns, representing 91 million individuals, will face a zero or negative tax liability. That's out of a total of 136 million federal tax returns that will be filed. Adding to this figure the 15 million households and individuals who file no tax return at all, roughly 121 million Americans—or 41 percent of the U.S. population—will be completely outside the federal income tax system in 2006.1 This total includes those who pay no tax, and those who pay some tax upfront and are later refunded the full amount of the tax paid or more.