Figure of 11.6 million seem low? See bottom of post. I added a link to a 2005 Bear Stearns report where they estimated that there may be up to 20 million illegals in the U.S.

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Sept. 1, 2007, 12:15AM
Federal count of illegal immigrants put at 11.6 million
Federal estimate matches figures commonly used

By HERNAN ROZEMBERG
San Antonio Express-news

The federal government quietly acknowledged Friday that the estimated count of people it has failed to stop from entering the country illegally has ballooned to nearly 12 million.

The Department of Homeland Security's Office of Immigration Statistics released a report indicating that, after crunching its statistics in combination with population counts from the Census Bureau, the country was home to 11.6 million "unauthorized" immigrants as of January 2006, including 1.6 million in Texas.

Russ Knocke, Homeland Security's press secretary, said the numbers simply recognize the U.S. economic pull that must be dealt with if there is an overhaul of the immigration system, including increased border security and a temporary worker program.

37% increase since 2000
The estimate matches the most commonly used count of 11.5 million to 12 million, issued two years ago by Jeffrey Passel, a veteran demographer with the Pew Hispanic Center.

The government report noted that illegal immigration jumped 37 percent from its previous estimate of 8.5 million in 2000. The results also paralleled previously established trends on migrants' nationalities and where they're settling.

Most are from Mexico
Mexico retains its top spot, responsible for 6.6 million of its citizens living illegally north of the border, up from 4.7 million in 2000, meaning that 315,000 Mexicans crossed annually.
Next up was El Salvador, with 510,000, followed by Guatemala with 430,000. But the largest percentage increase came from India, which saw its illegal population swell 125 percent, from 120,000 to 270,000.

Traditional destinations such as California, Texas and Florida still topped the list, but states like Georgia with 490,000 unauthorized migrants and North Carolina with 370,000 cracked the top 10.

The government report, as those issued by Passel and others, came with various disclaimers noting that estimates were rough due to various factors and assumptions that could make numbers go up or down.

"The government's figure is on the conservative side, but the actual number isn't as important as realizing we simply have a huge problem and something needs to be done," said Ira Mehlman, spokesman for the Federation for American Immigration Reform, the nation's largest restrictionist group with a claimed membership of 250,000

http://www.chron.com/disp/story.mpl/nation/5100287.html

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Bear Stearns report:

http://www.bearstearns.com/bscportal/pd ... ground.pdf