SAN DIEGO (AP) - President Donald Trump's plan to erect a wall along the Mexican border overlooks a key change in how people enter the U.S. illegally: Many of them make no attempt to jump a fence or evade authorities; they simply turn themselves in and ask for asylum.
Asylum requests have surged in recent years, especially since 2014, when families and unaccompanied children fleeing drug violence in Central America overwhelmed agents in Texas.
Those who express fear of returning home are often freed into the U.S. with a notice to appear before an immigration judge. It often takes years for the clogged courts to decide asylum cases.
"Migration is very, very different now," Gil Kerlikowske, commissioner of U.S. Customs and Border Protection from 2014 until last week, said Thursday. "People are coming up to our ports of entry, walking up and asking for some type of protection."
CBP does not release numbers on how many migrants turn themselves in versus how many are caught trying to avoid capture, but a pronounced shift is underway.
Longtime Border Patrol agents say their jobs are increasingly about changing children's diapers in holding facilities rather than chasing people through mountains and deserts.
Mark Morgan, who resigned under pressure Thursday as the Border Patrol chief only seven months after his appointment, told a Senate panel last month that he never thought buying baby powder and baby wipes would be part of his job.
"I just got from one sector where agents, one of their jobs during the day, is to actually make sure that the food, the burritos that were provided, are being warmed properly," Morgan said. "It takes a tremendous amount of resources to do this."
The 2,000-mile border has about 700 miles of fence, much of it built in California and Arizona during the second term of President George W. Bush, when crossers were predominantly Mexican men.
But that, too, has changed. In 2014, the number of Central Americans stopped by the Border Patrol surpassed the number of Mexicans for the first time. Many of them were women and children who turned themselves in. Also, a Pew Research Center study in 2015 found that more Mexicans were leaving the U.S. than entering, a dramatic reversal.
Border Patrol arrests - a key measure of illegal crossings - rose 23 percent to 415,815 during the 12-month period that ended Sept. 30, up from a 44-year-low in the previous year. Still, it was the fifth-lowest tally since 1972 and was down 75 percent from a peak of nearly 1.7 million in 2000. Border arrests include some migrants who turn themselves in and ask for asylum.
A consultant's report last year for the Homeland Security Department said asylum-seekers peaked in 2014 at 170,000, nearly triple the previous year's 63,000. Before 2012, there were fewer than 30,000 a year. Last year's caseload for asylum officers who do the initial screenings was more than 16 times what it was in 2009.
Many asylum-seekers turn themselves in to inspectors at land crossings or to Border Patrol agents almost immediately after setting foot in the U.S.
Trump has also pledged to stop "asylum fraud" and end what he and other critics of President Barack Obama's border enforcement efforts call "catch and release," or the practice of freeing people with a notice to appear in court. He hasn't provided details on how he plans to do that.
Eric Olson, director of the Wilson Institute's Latin America program, said additional fencing and Trump's pledge to add 5,000 Border Patrol agents to the current force of about 20,000 are bound to be a deterrent.
But he said those steps don't address issues like people who enter the country legally and overstay their visas or those who turn themselves in.
"Will it solve the problem?" Olson said. "I think it's clear that it really won't."