The proportion of all legal foreign-born residents who have become naturalized U.S. citizens rose to 52% in 2005, the highest level in a quarter of a century and a 15 percentage point increase since 1990.

Analysis of the March 2005 Current Population Survey shows that there were 11.1 million unauthorized migrants in the United States a year ago.

The number of migrants coming to the United States each year, legally and illegally, grew very rapidly starting in the mid-1990s, hit a peak at the end of the decade, and then declined substantially after 2001.

Most of the unauthorized population lives in families, a quarter has at least some college education and illegal workers can be found in many sectors of the US economy.

The undocumented population of the US now numbers nearly 11 million people, including more than 6 million Mexicans according to new estimates based on the most recent official data available.