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Illegal immigrants in the US: How many are there?

By Staff writer of The Christian Science Monitor / May 16, 2006

No matter how the Bush administration and Congress act on illegal immigration in the US, any legislation or executive order is unlikely to answer the question: How many immigrants living in the country today are here illegally?

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Depending on the source, the numbers range widely - from about 7 million up to 20 million or more.

Nailing down such figures is impossible. Even settling on a ballpark figure is difficult given the official sources: the US Census, apprehensions along the US-Mexico border, and social service agencies. For one thing, illegal immigrants avoid responding to census questionnaires, states a 2005 report by Bear Stearns Asset Management Inc. in New York.

Based on the national census in 2000, the US Census Bureau puts the estimate of illegal immigrants at 8.7 million. As of 2003, the US Citizenship and Immigration Services put the number at 7 million. Since then, United States immigration officials have said the number has grown by as much as 500,000 a year.

Those closest to the fight to protect US borders say the figure is higher. The US Border Patrol union Local 2544 in Tucson, Ariz., says the total number of illegal immigrants in the US today is between 12 million and 15 million.

The Pew Hispanic Center, a nonpartisan research organization in Washington, estimates 11.5 million to 12 million "unauthorized migrants" live in the US today. It bases its numbers on the "Current Population Survey," a monthly assessment of about 50,000 households jointly conducted by the US Bureau of Labor Statistics and the Census Bureau.

But in a letter to a constituent in 2004, Sen. John McCain (R) of Arizona wrote: "According to the US Border Patrol apprehension statistics, almost four million people crossed our borders illegally in 2002." Although many are caught and made to leave the country, a significant number try again. No one knows for sure how many succeed, but Senator McCain's assertion would mean that the number crossing the border and disappearing into the US economy could be much higher than official estimates.

"Deriving estimates of the number of unauthorized, or illegal, immigrants is difficult because the government lacks administrative records of their arrival and departure, and because they tend to be undercounted in the census and other surveys of the population," wrote the Congressional Budget Office in 2004.

Citing school enrollments, foreign remittances, border crossings, and housing permits, researchers at Bear Stearns reported "significant evidence that the census estimates of undocumented immigrants may be capturing as little as half of the total undocumented population."

There may be as many as 20 million illegal immigrants in the US today - more than twice the official Census Bureau estimate, according to Bear Stearns researchers Robert Justich and Betty Ng.