Bachmann's claim that undocumented immigrants cost taxpayers $113 billion each year, the Center for Immigration Studies puts that number at closer to $50 billion. That's before you consider the $11.2 billion they pay in taxes each year.

But Reason Foundation's Shikha Dalmia says that those numbers don't tell the whole story.

"Since undocumented workers have only fake [Social Security] numbers, they'll never be able to collect the benefits these taxes are meant to pay for," Dalmia wrote in 2006. "Last year, the revenues from these fake numbers — that the Social Security administration stashes in the 'earnings suspense file' — added up to 10 percent of the Social Security surplus. The file is growing, on average, by more than $50 billion a year."

According to the non-partisan National Resource Council, undocumented immigrants contribute $80,000 more in taxes than they consume.