The share that has been in the country at least 15 years has more than doubled since 2000, when about one-in-six or 16 percent unauthorized adult immigrants had lived here for that duration. By the same token, the share of unauthorized adult immigrants who have lived in the country for less than five years has fallen by half during this period—from 32 percent in 2000 to 15 percent in 2010.
The decrease has occurred in part because of reduced flows into the U.S. among Mexicans, who constitute 58 percent —or 6.5 million—of the unauthorized immigrant population. About 150,000 unauthorized immigrants from Mexico came annually to the U.S. from March 2007 to March 2009, down 70 percent from the annual rates during the first half of the decade. As for outflow, the number of Mexican migrants who voluntarily return to Mexico has stayed somewhat steady but deportations that are on the rise. There were almost 390,000 removals or deportations in fiscal 2010, or more than twice as many as in 2000, according to the Department of Homeland Security. About 73 percent of deportees in 2010 originally came from Mexico.
Much of this disparity results from the fact that unauthorized immigrants are younger than other groups of adults in the U.S. and more likely to be in their child-bearing and child-rearing years. The median age of unauthorized immigrant adults is 36.2 years old, which is about a decade younger than the median age of legal immigrant adults 46.1 and U.S. native adults 46.5.
Source: Pew Hispanic Center’s, “Unauthorized Immigrants: Length of Residency, Patterns of Parenthood”, December 2011.