Middle-class Americans--not the rich or the poor--pay the majority of annual tax revenues taken in by the federal government, according to data released in a new Congressional Budget Office study. Households earning less than $34,300 per year, meanwhile, actually pay a negative average federal income tax rate. Middle-class households that earned between $34,300 and  $141,900 paid 50.5 percent of all federal tax revenues in 2007 (the most recent year analyzed), according to the CBO study released Thursday, and households that earned between $34,300 and $352,900 paid 66.7 percent of all federal taxes.