The conservative Heritage Foundation released a report on Monday analyzing future costs of households headed by workers without a high school diploma. Data from 2004 shows that 50 percent of illegal workers fall into that category. The data also indicate that such households consume more in benefits than they pay in taxes.

"Each low-skilled immigrant household that gets amnesty costs the American taxpayers nearly $20,000 each year if we consider only the illegal aliens given amnesty." said Sen. Jim Bunning, R-Ky. "Those costs will add up to over $2 trillion — that's with a 't' — trillion over their lifetime."

The Senate voted Wednesday to slash the number of foreign workers who could come to the U.S. on temporary visas as part of a broad bipartisan immigration bill.

A new guest worker program would be capped at 200,000 a year under the proposal, which passed 74-24 over strong opposition by the Bush administration.