“As of today, we have cut the flow of immigration by over half.”

Immigration has been one of the toughest issues for Vice President Kamala Harris to address on the campaign trail; her opponent, Donald Trump, has repeatedly spotlighted a spike of illegal immigration under her and President Joe Biden. 

But in a recent CNN town hall in Delaware County, Pennsylvania, Harris offered an optimistic data point.

“As of today, we have cut the flow of immigration by over half,” Harris told moderator Anderson Cooper  Oct. 23. 

She’s right. Depending on when you start counting, the drop is well over half.

The night of the town hall, Harris’ campaign pointed PolitiFact to official federal government data on encounters at the United States’ southwestern border with Mexico. 

Encounters are occasions when immigration officials stop someone at the border. A single person could be stopped more than once and counted more than once, and encounters do not mean that the person is let into the U.S. But for understanding migration at the U.S. border, encounters are a standard metric.

Border Patrol encounters with migrants between ports of entry at the southwest land border peaked in December 2023 at about 250,000. In September, the latest month with available data and the end of fiscal year 2024, there were about 54,000 encounters. That’s a 78% drop, or more than half, U.S. Customs and Border Protection data shows.

If you start with a different month, the drop is still significant. From September 2023 to September 2024, the number fell from about 219,000 to 54,000, a 75.3% decline. From January 2024 to September 2024, the number fell from about 124,200 to 54,000, a 56.5% drop.

U.S. immigration experts said it’s difficult to isolate single causes for changes in border arrival counts, but a Biden executive action that limits immigrants’ ability to apply for asylum at the southwest border took effect in June and likely has had an effect.

“The Biden playbook rests on narrowing asylum eligibility for migrants who cross the border illegally, expanding the use of lawful migration pathways, and encouraging Mexico, Panama, Costa Rica, and other regional partners to increase their migration controls and enforcement,” the Migration Policy Institute, a nonpartisan think tank, wrote in a recent analysis.

Taken together, the group added, “these policies have ushered in a new era of migration management in response to unprecedented changes in flows over the last three and a half years. These efforts represent new and innovative approaches to managing migration, even as they are subject to litigation and change.”

Mexican efforts to increase its enforcement, driven partly by U.S. pressure, have also helped decrease immigration, experts say. 

Biden and former Mexican President Andrés Manuel López Obrador spoke multiple times beginning in late 2023 and released statements about joint efforts to curb immigration, fentanyl and firearms trafficking.

U.S. Homeland Security Secretary Alejandro Mayorkas and Secretary of State Antony Blinken also went to Mexico in December to meet with their Mexican counterparts. 

David Bier, immigration studies director at the libertarian Cato institute, told PolitiFact in June that it’s reasonable to attribute border encounter declines to actions by Mexico, with a caveat.

“Mexico is making unprecedented arrests,” Bier said. “I believe that it is unsustainable because, although Mexico is arresting them and sending them to southern Mexico, they are not deporting them to their home countries. This means that it is very likely they will ultimately find their way to the United States because they are still in Mexico, and there’s not much for them to do there except keep trying to get to the U.S.”

Whether the declines will continue is uncertain, because migrants and migrant smugglers “have proven highly adaptable to changes in policy, process, operations and even infrastructure,” Theresa Cardinal Brown, senior adviser for immigration and border policy at the Bipartisan Policy Center, a think tank, told PolitiFact in June. “We have not seen sustained decreases in arrivals after policy changes in the past.”

Our ruling

Harris said, “As of today, we have cut the flow of immigration by over half.”

The size of the drop varies depending on what month you start counting from, but over roughly the past year, the number of encounters along the southwestern U.S. border has declined from 57% to 78%.

We rate the statement True.

PolitiFact Staff Writer Maria Ramirez Uribe contributed to this report.