The population of illegal immigrants in the U.S. has stabilized at 11.2 million since the Great Recession, according to a new report, with their numbers declining in 14 states and rising in seven states from 2009 to 2012.
The independent Pew Research Center, which analyzed census data, concluded that the leveling off of the undocumented population nationally is a direct result of the shrinking of the undocumented Mexican population in the U.S. That trend was offset by a recent increase in illegal arrivals from Central America.
“The Mexican numbers have been going down significantly even as the national number of unauthorized immigrants remained constant,” said Jeff Passel, the center’s senior demographer. That resulted from both an increase in departures to Mexico and a decrease in arrivals from that country.
Since 2007, there have been more people leaving the U.S. for Mexico than coming here from Mexico, Mr. Passel said. Those departures have been both voluntary and involuntary, as the Obama administration has deported hundreds of thousands of undocumented immigrants each year.
Between 1998 and 2001, Mexicans were arriving at the rate of 700,000 each year to take jobs in construction, hospitality and other low-skilled sectors. That rate plummeted to 140,000 from 160,000 between 2011 and 2012.
Mexico has been the top source of undocumented immigrants to the U.S. at least since 1995, when Pew began tracking migratory trends. In a reversal, about 80% of Mexican immigrants entered the U.S. illegally then; today 80% of them enter legally. In 2012, there were 5.9 million undocumented Mexicans in the U.S. compared with seven million in 2009.
The undocumented population, which has triggered heated national debate, peaked at 12.2 million in 2007.
The debate flared anew recently when President Barack Obama restated his intention to take executive action to provide relief from deportation and work permits to millions of people living in the U.S. illegally. Republican leaders, who will control the House and Senate next year, have questioned his authority to take such action.
Arizona, Nevada and Georgia, where construction withered amid the mortgage crisis, are among states where the undocumented population declined between 2009 and 2012, according to the report.
“All indications are that the big pre-recessions flows created an oversupply of cheap immigrant labor, particularly in home construction,” said Roberto Suro, director of the Tomas Rivera Policy Institute at the University of Southern California.
In Mexico, pressures that previously compelled people to seek work in the U.S. have eased. For instance, Mexico’s economy has been absorbing larger shares of new entrants to the labor force than in the late 1990s or before the U.S. recession. Mexican families are smaller, which also induces fewer workers to journey North to earn hard currency. They also have been deterred by gangs that sometimes extort money from migrants, and have killed some people en route to the U.S.
But pressures are unrelenting in other countries, propelling people from impoverished and violence-racked El Salvador, Guatemala and Honduras to attempt to reach the U.S. “The fact that those Central Americans keep coming ought to be a reminder that when people are driven, they will make the trip despite substantial costs and dangers,” Mr. Suro said.
Over the summer, a surge in mothers and children coupled with record numbers of unaccompanied minors from those countries reaching the Southwest border created a domestic political crisis. Many Republicans said the wave proved the need to further bolster border security before Congress can consider any overhaul to legalize undocumented immigrants in the U.S.
In five eastern states, including Maryland, New Jersey and Virginia, the increase in the number of undocumented immigrants was fueled by non-Mexican arrivals, according to the Pew report.
California, Florida, Illinois, New Jersey, New York and Texas are home to more than half of the undocumented population.
The 8.1 million undocumented immigrants who were working or looking for work in 2012 represented 5.1% of the labor force. Their share of the labor force was highest in Nevada in 2012, at 10.2% of the total.
In states where undocumented immigrants represent a small share of the overall population, such as Alabama, Georgia and South Carolina, their presence has especially fueled controversy. “If you look at what share the unauthorized make up of the total workforce or their numbers relative to the population in these states, they definitely are not big,” Mr. Passel said.
Write to Miriam Jordan at miriam.jordan@wsj.com