Arrests of illegal immigrants along the U.S. border with Mexico are at the lowest level since the Nixon administration, indicating that fewer people are attempting to cross the border to live or work in the United States.
The sixth consecutive annual decline in border crossings could change the debate on illegal immigration from securing the border to handling the people who are already here illegally.
"Increasingly, the problem is the 11 million people [in the country illegally] rather than the border itself," said Demetrios G. Papademetriou, president of the Migration Policy Institute, a nonpartisan research organization.
In the fiscal year that ended Sept. 30, Border Patrol arrested 327,577 people trying to cross the southern U.S. border. Meanwhile, Immigration and Customs Enforcement officials deported a record 396,906 people in the same period. That marks the first time in decades that formal removals from the U.S. outpaced arrests at the border.
The number of arrests of people trying to sneak across the border has been steadily declining since 2006, after an all-time high of more than 1.6 million apprehensions in 2000. During those 10 years, more immigrants have become settled residents of the U.S.
According to the Pew Hispanic Center, nearly two-thirds of the country's estimated 10.2 million adult illegal immigrants have been living in the U.S. for at least 10 years. A decade ago, less than half had been in the U.S. that long.
"This is all part of a larger picture that we're not seeing very many new undocumented immigrants coming in, so the share of new undocumented immigrants is smaller," said Jeffrey Passel, senior demographer at the Pew Hispanic Center. "A lot of people are staying. They've put down roots. There clearly hasn't been a large-scale departure of people who have been here awhile."
But politicians are still fighting over who is best equipped to secure the border.
Attempts to pass immigration-reform legislation have repeatedly failed, with Republicans saying they won't support any bill that provides a path to legalization for illegal immigrants who are here and won't consider other reforms until the border is secure.
But the weak U.S. economy and tough new immigration laws in states such as Alabama and Arizona likely play as much of a role in the drop in illegal crossings as increased security efforts, said Doris Meissner, former head of the Immigration and Naturalization Service and a senior fellow at the Migration Policy Institute.
"There is no single thing we can point to," she said. "I think it's perfectly legitimate to say that border security is working. But it is not legitimate to say they are entirely responsible. Obviously, it's a combination of the economy and enforcement."
Republican strategist Danny Diaz said the debate can't shift to the question of how to handle illegal immigrants living in the U.S. until Republicans are convinced the border is secure.
"I'm sure there is some credit that's [a result of enhanced security], but I don't think anyone would argue that the border is secure," Mr. Diaz said. "That's just not true. I believe if the economy was improved, those numbers would go up."