This just in from the non-partisan Tax Foundation:
Nearly one-third of the 143 million federal income tax returns filed in 2007 resulted in no tax payment, according to a Tax Foundation analysis of IRS data. That means the tax filers got back every dollar that had been withheld from their paychecks, and often more. Roughly 46.6 million tax returns, or 32.6 percent, are filed by such "nonpayers," people whose exemptions, deductions and credits wiped out any federal income tax due.
"In about half the cases, additional money was 'refunded' to these tax filers -- meaning they received a check from the government -- similar to welfare spending programs," said Tax Foundation President Scott Hodge, who authored Tax Foundation Fiscal Fact No. 202, "Surge of 'Nonpayers' Will Be Part of Bush Tax Legacy.