About 11 million illegal immigrants were living in the U.S. at the start of this year, the federal government said in a report Friday.
That's up from an estimated 8.5 million living in the country in January 2000, according to calculations by the Office of Immigration Statistics in the Department of Homeland Security.
The office estimated that 10.5 million illegal immigrants were living in the United States in January 2005 and that the number grew at a national average of 408,000 a year.
Estimates of the size of the illegal immigrant population vary widely according to the political leanings of groups using them.
The federal government acknowledged the difficulty of getting an accurate count in its report, saying estimates involve assumptions and combinations of data.
A Homeland Security spokeswoman could not be reached immediately.
In March, the Pew Hispanic Center used Census Bureau data to estimate that the United States had 11.1 million illegal immigrants in March 2005. The center used monthly population estimates to project a total of 11.5 million to 12 million in March.
Mexico is the largest contributing country of illegal immigrants, with nearly 6 million in the U.S. in 2005, the government said. El Salvador, Guatemala, India and China followed with a combined contribution of about 1.4 million unauthorized immigrants.
The greatest increase in illegal immigrants in the country was among Mexicans, a jump of 260,000 from 2000 to 2005. The greatest percentage increase in the immigrant population in those years was among people from India, 133 percent, and Brazil, 70 percent.
California had the largest illegal immigrant population, with 2.8 million in January 2005, followed by Texas with 1.4 million and Florida with 850,000.