If there’s one thing that Democrats and Republicans agree on, it’s that Trump deserves credit for closing the southern border—and that the Biden administration is to blame for the mass border crossings of 2021–2023. Several recent retrospectives in the New York Times are the latest in a line of pieces cataloguing the Biden administration’s costly mistakes at the border.
The story of these mistakes seems simple. Border crossings swelled when Biden took office and plunged when he left. Right?
Wrong. In fact, the Biden-era spike in border crossings started before Biden took office and ended before he left office
But the myth persists because Americans like to assume that our border policy drives migration, and not the other way around. In a new working paper that draws on detailed data from Customs and Border Protection, we show that new restrictions on border crossings under both Biden and Trump had little immediate effect.
But it doesn’t take an academic study to know that this basic story about the border is wrong.
First, it doesn’t fit the timeline. As Figure 1 below shows, the spike in arrivals at the Southern border started in 2019 – during the first Trump administration, on the heels of that administration’s asylum restrictions and family separations. May 2019 saw more than 100,000 monthly border apprehensions for the first time in over ten years.
Figure 1: 25 Years of Apprehensions at the Southern Border
Moreover, the spike ended during 2024: between December 2023 and December 2024, monthly apprehensions fell from roughly a quarter million to about 50,000 (see Figure 2). The numbers have fallen still further in 2025, to around 10,000 a month, but however you slice it, most of the decline happened on Biden’s watch.
Second, the Biden administration’s border policy was mostly more restrictive than the first Trump administration’s. For example, observers made much of the fact that Biden ended Trump’s Return to Mexico policy when he took office—but Biden kept in place the Title 42 policy of summary expulsions at the border. That meant that instead of being sent back to Mexico to wait for a court hearing (under the return to Mexico policy), asylum seekers were simply sent back to Mexico with no hope of a court hearing.
The simple story doesn’t fit the timeline and overstates the openness of Biden’s border policy. But more fundamentally, this simple story overestimates the importance of U.S. border policy itself.
To get a better grasp on the effects of restrictive border policies, we recently studied nine of the most prominent new enforcement actions of the last decade from Obama to Trump to Biden. We found few large, immediate effects on numbers at the border. Simply put, those policies are not the key drivers of migration into the United States.
Take President Trump’s notorious family separation policy. After that highly publicized policy took effect in spring 2018, arrivals of families did not plunge. And after President Trump announced its end, arrivals of families did not surge. Similarly, after the Supreme Court first allowed President Trump to end asylum at the border in September 2019, arrivals at the border remained steady.
When people flee their homes, they’re often not thinking about where they’ll end up. And when they make it to the border of the United States, they may decide to try their luck regardless.
We don’t mean to suggest that border policy never has effects. We find that two draconian policies—Biden’s 2024 policy of summary expulsions, and President Trump’s further tightening of that policy in January 2025—may have caused relatively small decreases in arrivals.
But these decreases were just that: small. The large trends of the last few years were about something other than U.S. border policy, and the unsatisfying fact is that we don’t know exactly what. Some migrants fled violence and drought. High demand for employees in the United States after the pandemic might have attracted others. And migration can snowball: once a few people started crossing the Darien Gap, the jungle between South and Central America, that route became more accessible, and many others followed.
Migration to the United States has a lot less to do with U.S. border policies than policymakers or the public would like to think. That truth hasn’t stopped the current administration from declaring a war on immigrants. But cruel immigration policies don’t guarantee low border crossings. And if we have any hope of moving toward a constructive conversation about American immigration policy, we first have to stop giving both Trump and Biden credit for the wrong things.
FEATURED IMAGE: Graph: Monthly border patrol apprehensions
Great Job Adam Cox & the Team @ Just Security for sharing this story.
