The Internal Revenue Service tracks the tax returns with the 400 highest adjusted gross incomes each year. The average income on those returns in 2007, the latest year for IRS data, was nearly $345 million. Their average federal income tax rate was 17 percent, down from 26 percent in 1992.
Over the same period, the average federal income tax rate for all taxpayers declined to 9.3 percent from 9.9 percent.
There are so many breaks that 45 percent of U.S. households will pay no federal income tax for 2010, according to estimates by the Tax Policy Center, a Washington think tank.