As the issue of immigration — legal or otherwise — gains traction in the 2016 presidential race, there's more evidence that illegal immigration is not only declining, but it's been on a decade-long downward trend.
"The undocumented population has essentially reached zero growth, " said Robert Warren, the author of a new report published by the New York-based Center for Migration Studies. "The population has stopped growing because slightly more people are leaving than are coming in from Mexico."
In fact, the number of unauthorized immigrants is about 10.9 million, the lowest since 2003, according to Warren. That's partly explained by the steady decline among the Mexican-born people living in the U.S. without permission, which has fallen by more than a million since 2008.
Warren has been crunching immigration numbers for more than four decades, including 35 years at the U.S. Census Bureau and what used to be called the Immigration and Naturalization Service. His findings are consistent with the conclusions of other researchers.
Among his other findings, Warren said that California, New York, and Illinois saw the greatest declines between 2010 and 2014. Of the 10 states with the highest populations of people immigrating illegally — California, Texas, New York, Florida, Illinois, New Jersey, Georgia, North Carolina, Arizona and Virginia — only Texas and Virginia gained such residents between 2010 and 2014.
And while so much of the current debate in Washington and around the country is focused on illegal immigration, Warren found that legal immigration is equally notable. "From 1980 to 2014, the legally resident population from Mexico grew faster than the Mexican undocumented population," he wrote.
In an interview, Warren told NPR that the naturalized population — people who have become citizens — has been increasing by at least 10 percent in every state for the last eight years.
Still, it's illegal immigration that gets all of the attention, said Warren even though he thinks the net zero growth in the unauthorized population will be a long-term trend given the tough security measures at the U.S.-Mexico border and the health of the Mexican economy.