The number of unauthorized immigrants peaked in 2007 at 12 million, and the decline since then has been the first significant decrease following two decades of growth.
The decline of unauthorized immigrants has been driven mainly by a decrease in the number of new immigrants from Mexico, the single largest source of U.S. migrants. The Pew Hispanic Center reported that net immigration from Mexico to the United States has stopped and possibly reversed through 2010. The standstill appears to be the result of many factors, including the weakened U.S. job and housing construction markets, heightened border enforcement, a rise in deportations, the growing dangers associated with illegal border crossings, the long-term decline in Mexico’s birth rates and broader economic conditions in Mexico.
The U.S. today has more immigrants from Mexico alone—12.0 million—than any other country in the world has from all countries of the world. Some 30% of all current U.S. immigrants were born in Mexico.
In addition, the number of Mexicans and their children who moved from the U.S. to Mexico between 2005 and 2010 roughly doubled from the number who had done so in the five-year period a decade before.
In early 2013, the Pew Hispanic Center plans to release an estimate of the 2012 U.S. unauthorized immigrant population.
Source: The Pew Hispanic Center, Unauthorized Immigrants: 11.1 Million in 2011, December 6, 2012.