Illegal border crossings in Arizona “plunged” in December of 2019, according to the Associated Press, dropping a staggering 90% year-over-year following a Trump administration change in policy that has asylum seekers waiting for their adjudication hearings in Mexico and not in the United States.

Last winter, a “record number” of illegal border crossers were apprehended in the Arizona sector of the United States-Mexico border, with 60,000 migrants taken into United States Border Protection custody in December of 2019 alone, per the Washington Examiner. That was the beginning of a surge migrants crossing the United States’ southern border; by May of 2019, the Border Patrol was recording a record number of apprehensions every month, sometimes topping 100,000.

“50,753 people were arrested for trespassing from Mexico in December. It marks the third month in a row that more than 50,000 people have illegally crossed into to the U.S. Another 10,000 people who tried to enter through ports were told they lacked the documents to do so,” according to the Examiner. “Illegal immigration apprehensions at the southern border have skyrocketed since Trump’s first few months in office, when 15,000 to 20,000 people were reported being apprehended per month.”

In Arizona alone, the Border Patrol was registering around 14,000 apprehensions per month by May of 2019, but in October of 2019, there were only 800 apprehensions. In December of 2019, the streak kept up, and apprehensions dropped around 90%.

The Border Patrol credits the Trump administration’s new “remain in Mexico” policy, which requires those who want to seek refuge from violence and disorder by emigrating to the United States to stay south of the border until their asylum case comes before a judge. Before that policy took effect, asylum seekers were given a piece of paper with a court date and then released into the United States to stay with friends and family until they had to appear before a judge.

By the time their cases rolled around — sometimes two to three years after apprehension — most asylum-seekers were in the wind, impossible to find, and well-integrated into American life.

“Arrests in the Border Patrol’s Yuma sector nearly hit 14,000 in May, when the policy to make asylum-seekers wait in Mexico took effect there. By October, they fell 94%, to less than 800, and have stayed there since, making Yuma the second-slowest of the agency’s nine sectors on the Mexican border, just ahead of the perennially quiet Big Bend sector in Texas,” the AP reported.

“Illegal crossings in western Arizona have swung sharply before, and there are several reasons for the recent drop. But Anthony Porvaznik, chief of the Border Patrol’s Yuma sector, said the so-called Migration Protection Protocols have been a huge deterrent, based on agents’ interviews with people arrested,” the outlet added.

“Their whole goal was to be released into the United States, and once that was taken off the shelf for them, and they couldn’t be released into the United States anymore, then that really diminished the amount of traffic that came through here,” Porvaznik said.

So far, the courts have largely upheld the president’s policy. In California, a court did order that asylum seekers be provided with access to an attorney before being sent back, and the courts have also suggested that those apprehended by Border Patrol be processed within 72 hours. Some waited “up to a week” in Yuma before being sent on.