The number of illegal immigrants living in the U.S. has steadily declined over the past three years, as a weakened economy and tougher enforcement of immigration laws deterred some would-be migrants and spurred others to return home.
But that trend has come to an end, at least temporarily, according to a new analysis of Census Bureau data by the Pew Hispanic Center.
There were an estimated 11.2 million undocumented immigrants living in the U.S. in March, 2010, the Pew report finds, a number statistically unchanged from the year before.
"The U.S. economy is still doing better than the Mexican economy, and the figures suggest these immigrants are finding enough here to hang on," said Pew demographer Jeffrey Passel. "The downward trend may have lost steam. They've invested a lot of effort and money to get to the U.S. and this suggests they aren't going to leave easily."
The study found that the number of children born to one or more illegal immigrants on U.S. soil also held steady last year. The children have been at the center of the recent debate over birthright citizenship and the 14th Amendment to the Constitution, to which several GOP lawmakers have proposed a change.
Roughly 350,000 newborns, or 8 percent of all births in 2010, had at least one parent who was not in the U.S. legally.
The report's snapshot of the U.S. illegal immigrant population highlights a politically thorny issue that continues to fester across the country, despite promises by members of Congress and the Obama administration to address it.
"We should take on, once and for all, the issue of illegal immigration," President Obama said last week in his State of the Union address. "I am prepared to work with Republicans and Democrats to protect our borders, enforce our laws and address the millions of undocumented workers who are now living in the shadows."
Meanwhile, several GOP lawmakers have proposed redoubling security measures along the southwest border and revising the Constitution to deny citizenship to U.S.-born children of illegal immigrants. Several state legislators are also exploring similar bills.
The total number of children born to undocumented immigrant parents and living in the U.S. as of March 2010 was 4.5 million, according to the Pew study.
The report also notes that the geographic distribution of the nation's illegal immigrant population is changing.
Four states -- Florida, New York, Virginia and Colorado -- experienced continued decline in their illegal immigrant populations through 2010. Arizona, Nevada and Utah, combined, also saw a statistically significant decrease, the report found.
Three south-central states -- Louisiana, Oklahoma and Texas -- saw a net influx in illegal immigrants in 2010, however. An estimated 1.55 million illegal immigrants lived in that tri-state region in 2007; the number grew to 1.8 million in 2010.
Economy, Enforcement Cited for Decline
Passel said the recent declines have been led by the departure of a significant number of Mexican illegal immigrants, who have traditionally made up the majority of the U.S. undocumented population.
Experts say many may have returned voluntarily because of disparate work in the U.S. due to the down economy. But enhanced enforcement of U.S. immigration laws is also widely cited as an explanation for the decline.
The number of apprehensions along the southwest border -- the best indicator of illegal flows -- has fallen 36 percent over the last two years, according to the Department of Homeland Security. The agency has also deported record numbers of illegal immigrants already inside the U.S. for each of the past seven years.
"The Obama administration has engaged in an unprecedented effort to bring focus and intensity to Southwest border security," said Homeland Secretary Janet Napolitano Monday in remarks in El Paso, Texas. "Almost two years into the Southwest Border Initiative and the verdict is in: our approach is working -- illegal immigration is decreasing, deportations are increasing and crime rates have gone down."
Passel said that a forecasted "dramatic decline" in the Mexican birth rate could mean fewer babies, fewer people looking for jobs and potentially fewer migrants seeking to enter the U.S. in the years ahead.
But, he added, if history is any guide, as the U.S. economy recovers, illegal immigration levels may again begin to rise.
"That's what's happened before," said Passel. "Over the last 15 years, when the U.S. economy has been strong and growing, we've seen increases in undocumented immigrants in this country."