In 1960 only 15% of federal income tax returns had a zero tax liability, due mostly to low taxable income, a standard deduction, the personal exemption, the dependent exemption, and the Earned Income TaxCredit (a direct subsidy to people for being poor).
Mr Bush is therefore proposing to introduce a taxcredit which would allow people to direct their tax payments to charities rather than to the government.
This week the Supreme Court rejected that equivalence, ruling that an Arizona taxcredit differed enough from a comparable direct spending program to deny taxpayers the right to sue on the basis that the credit represented an unconstitutional government activity.