The debate over immigration reform resumes on Capitol Hill this week — so brace for a barrage of conflicting claims over whether the millions of people here illegally drain or fill the government's wallet.
Illegal immigrants cost $20 billion each year in education, health care and other public services. They contribute more than $7 billion annually in Social Security taxes for benefits they'll never claim.
Those are just some of the statistics that lawmakers and interest groups from both sides will trot out starting Monday when the Senate begins discussing what would be the most sweeping immigration reform legislation in 20 years.
Do illegal immigrants take more than they contribute? Or is it the other way around?
Despite volumes of studies cited by both sides, no one knows for sure.
And answers often reflect the opinions of who's talking as much as the reality of illegal immigrants in the United States today, according to academics who study the issue.
"Because of the politically charged nature of this, people are going to cherry-pick their results," said V. Joseph Hotz, a labor economist at the University of California, Los Angeles, who doesn't believe a definitive study is possible.
‘Data is going to be suspect’
One reason is the nature of the population in question.
"Anything that is illegal, the data is going to be suspect," said Vernon Briggs, a labor economist at Cornell University who has been studying immigration issues for 40 years.
That won't stop Congress from wrestling with that bottom line and other issues.
Majority Leader Bill Frist, R-Tenn., has said he is committed to passing immigration reform legislation by Memorial Day. The bill up for debate would include additional border security, a new guest worker program and provisions opening the way to eventual citizenship for many of the illegal immigrants in the country.
The House passed a bill late last year that would criminalize illegal immigrants and those who offer them assistance.
Pressure to act quickly has intensified. A majority of Americans now cite anxiety over immigration as one of the most important problems facing the nation, according to a recent poll by The Associated Press and Ipsos.
11 million, or 20 million?
Yet compiling hard data has been difficult.
Even the number of illegal immigrants in the country is debated. The generally accepted figure is about 11 million, but some researchers peg the number as high as 20 million.
In diverse areas such as Los Angeles, illegal immigrants can rent an apartment and open a checking account with little more than an ID from their home country. That kind of anonymity hampers researchers trying to tally how many are here — and how much they cost in public services.
That uncertainty hasn't stopped advocates on both sides from citing research that seems to make their case.
To fill in the blanks, researchers often assume the bulk of illegal immigrants have little or no formal education or skills; are likely to live at or below the poverty level; contribute little in the form of taxes; and take advantage of public services.
State vs. federal
One report both sides cite as one of the most definitive is nearly a decade old. In 1997, the National Research Council concluded that all immigrants — not just those here illegally — had a negative fiscal impact on state and local services but at the federal level received less in services than they paid in taxes.
In California, the state with the highest population of foreign-born residents, citizen households were saddled with an annual tax burden of $1,178 from the use of public services by immigrants, according to the study.
Pro-immigrant groups counter that whatever the answer — whether immigrants pay more in taxes than they use in services or the other way around — the economic importance of illegal immigrants is undeniable.
"You don't know whether a guy who is loading boxes on a truck or onto a ship on the docks pays his taxes or not," said Benjamin Johnson, director of the Washington-based Immigration Policy Center, which calls itself nonpartisan but pro-immigrant. "But you know what that worker means as a cog on the economic wheel."