Just in time for tax filing season, the Tax Foundation and Congress's Joint Committee on Taxation have compiled some useful facts about the federal tax system. Following are a few worth thinking about as taxpayers write their annual checks to Uncle Sam.

-- In 2005, the federal government took $2.4 trillion out of the pockets of the American people. To put this number into context, it is about the same as the size of the entire U.S. economy in 1959 in inflation-adjusted terms. Only two other countries on earth have economies as large as our federal government: Germany and Japan—and Germany just barely makes the cut, with a gross domestic product of $2.7 trillion. China, which everyone is so alarmed about, has an economy significantly smaller than the federal government, with a GDP of $1.9 trillion—about equal to what the U.S. raises just from taxes on individuals.

-- Contrary to popular belief, the vast bulk of federal taxes are paid by the wealthy. According to the JCT, in 2006, 53.7 percent of all federal income taxes were paid by those with incomes over $200,000. Those with incomes between $100,000 and $200,000 paid 28.3 percent of all individual income taxes. Thus those with incomes over $100,000 paid 82 percent of the total. They also paid 44.4 percent of all payroll taxes.

-- Those with incomes below $40,000 paid no federal income taxes at all in the aggregate; the positive liability for those who paid anything was more than offset by tax rebates from the Earned Income Tax Credit for many more who paid nothing. In total, the EITC put $41 billion into the pockets of low-income workers in 2005, 91 percent of it being paid to those with no income tax liability. However, according to the Tax Foundation, three-fifths of Americans believe that it is wrong for anyone to pay no taxes at all, that everyone should pay something to finance the government.

-- So-called tax loopholes—deductions and exclusions that reduce one's tax liability—are mainly used by the middle class, not the wealthy. The largest tax expenditures are the exclusions for pension contributions and health benefits for workers. Among the largest deductions are those for mortgage interest and state and local taxes. In 2005, taxpayers saved $62 billion in taxes due to the mortgage interest deduction, with 72 percent of that going to those with incomes below $200,000. The child credit saved taxpayers $46 billion—almost all of it claimed by the middle class. Just $8 million went to those with incomes over $200,000.

-- Not surprisingly, three-fifths of taxpayers believe their taxes are too high; only two percent think they are too low. About a third of taxpayers would support a reduction in government services in order to achieve further tax cuts; just eight percent favor bigger government financed with higher taxes.

-- Support for fundamental tax reform is high; four-fifths of taxpayers believe that the tax system is too complex; just three percent believe the tax system is fine the way it is. By better than a 2 to 1 margin, taxpayers would be willing to give up major tax deductions, such as that for mortgage interest or state and local taxes, in order to get lower income tax rates.

-- Almost all taxpayers think that the top federal income tax rate of 35 percent is too high. More than 90 percent of taxpayers believe that the top rate should be no higher than 29 percent, with 70 percent saying that 19 percent should be the maximum.

-- The Alternative Minimum Tax is a rapidly growing federal tax. Originally designed to tax only the rich, increasingly it is a tax on the middle class. In 2005, the AMT affected only 1.3 percent of those with incomes between $50,000 and $100,000. Unless Congress acts, this percent will rise to 42.8 percent this year and over 50 percent next year. This illustrates the problem with all soak-the-rich tax proposals—eventually they end up taxing the middle class, too.

For years, Republicans have largely ignored the problem of the AMT—enacting temporary patches to the tax cut to keep the problem from getting worse, but not even attempting to offer a permanent fix. The latest patch expired at the end of last year, which is why there is such a sharp rise in the percentage of taxpayers affected by the AMT projected.

Consequently, Democrats really have a gun to the heads—they must do something on the AMT by the end of the year. But because they have pledged to pay for all tax cuts, they must therefore raise taxes somehow to pay for an AMT fix. Republicans aren't likely to offer much help in that area, making tax policy in 2007 an interesting spectator sport.