What Congress does—or doesn't do—about the Bush tax cuts and how it will affect you.

Some things never change. The current Republican leadership, like the Republican leadership of the early aughts, likes tax cuts—the broader the better. The current Democratic leadership, meanwhile, doesn't want to be accused of raising taxes. Welcome to the dying days of the 111^th Congress, devoted to replaying the battles of the 107^th and 108^th.

The last big fight of this lame-duck session is over tax cuts passed in 2001 and 2003. Most Republicans would like to keep all of them. Most Democrats want to make the middle-class tax cuts—that's the term all sides are using for the parts of the law that affect individuals making less than $200,000 a year or families making less than $250,000—permanent. But they also want to let the breaks for the wealthiest 2 percent of Americans expire.

What is everyone bickering over? What does it mean for "middle-class Americans," the group every side is supposedly looking out for? Is Congress really raising taxes? Here, as a public service, are answers to these questions.

Last question first: Congress isn't really raising taxes. At least this Congress isn't. The 107^th and 108^th, back in the early aughts, passed this tax hike as part of a tax-cut bill. (Stay with me; it gets better.) Republicans wanted big, permanent tax cuts but lacked the votes to get them through the Senate. So they passed the two bills slashing taxes using the budget reconciliation process, which allows the party in power to avoid filibusters. Then they had to deal with something called the "Byrd rule," which lets senators block reconciliation legislation if it results in an increase in the deficit 10 years after its passage. Republicans handled that problem by simply writing an expiration date into the law: Jan. 1, 2011. The thinking was that no future Congress would dare allow taxes to go back up, and so these temporary cuts were really permanent.

On Thursday, President Obama plans to start negotiations on a compromise—which should be interesting, given that Congress has only about 35 working days before the cuts expire altogether. The current betting is that Congress will agree to extend the cuts for a year or two, and then figure out its next move later.

Still, given Congress' ability to not get things done, it may be worth considering what happens if it cannot come to an agreement. Starting Jan. 1, just about every taxpayer would see higher rates. Right now, income tax rates fall on a sliding scale from 10 percent to 35 percent. That scale would shift, with new brackets starting at 15 percent and going up to 39.6 percent.

It is a little hard to parse out the effects for average families—this tax law was complicated, as is the tax code. But the easiest way to understand how, and how much, taxes will go up is to look at average effective tax rates, the percentage of income that families and individuals pay—including taxes, deductions, exemptions, and everything else. The Tax Policy Center estimates that, if the Bush cuts expire, a family in the lowest income quintile would pay 5.2 percent of its income in federal taxes, rather than 4.6 percent, for the 2011 tax year. For a family in the top 20 percent of income, the jump would be from 25 percent to 28.3 percent.