Trump’s ban on travel from six Muslim majority countries, temporarily reinstated by the Supreme Court on Monday morning, is supposed to stop terrorists from getting in to the US. But there’s precious little evidence that immigrants and refugees actually pose a serious terrorist risk to the United States.

A September report, from Cato Institute analyst Alex Nowrasteh, is one of the most sophisticated attempts to investigate this question. What it found was striking: The number of immigrants who commit terrorist attacks is astonishingly tiny.

Cato is a libertarian think tank that has a noticeably pro-migration stance. But Nowrasteh’s research is on really solid ground: He combed through data on terrorism and immigration from nine different sources, covering 1975 through 2015. He counted any attack on US soil in which an immigrant participated as a terrorist attack by immigrants, even if some native-born Americans also helped in its planning or execution.

Virtually all the deaths from immigrant attacks (98.6 percent) came from one event: 9/11. Other than that, fatal immigrant-linked terrorist attacks in the US were vanishingly rare — and ones linked to refugees specifically rarer still.

The average likelihood of an American being killed in a terrorist attack in which any kind of immigrant participated in any given year is one in 3.6 million — even including the 9/11 deaths. That is a very, very, very low number.

To put that in perspective, I’ve produced the following chart, which compares the average annual likelihood of American pedestrians being hit by a railway vehicle, dying due to their own clothes melting or lighting on fire, and being killed in a terrorist attack perpetrated by an immigrant. It’s quite revealing:

If you exclude the 9/11 attacks from this data, you’re more likely to be killed by a lightning strike than a terrorist attack executed by foreigners — by a whole lot.

And 9/11-style attacks are far less likely today than they were before 9/11. These plots are intrinsically difficult to pull off: They require huge amounts of planning, organization, and preparation. This makes them much easier to detect than, say, a random person who decides to buy a gun — especially since the US government has devoted an extraordinary amount of resources since 9/11 toward disrupting plots abroad.

“15 years without a mass-casualty attack is more than luck,” Dan Byman, a terrorism expert at Georgetown University, writes for Vox. “The US government’s counterterrorism efforts — in the form of military strikes on terrorist infrastructure, CIA-led international intelligence cooperation, FBI domestic investigations, and Department of Homeland Security border security — deserve much of the credit.”

Later in the paper, Nowrasteh breaks down the numbers by visa status — whether the terrorist was here as a student, for example, or had a green card. The 9/11 attackers mostly came in on tourist visas.

But perhaps the most interesting breakdown concerns refugee visas. Despite all of the panic from Trump and Breitbart News about ISIS members sneaking in as refugees, this kind of thing is incredibly rare (partly because of the intense vetting that refugees, and Syrian refugees in particular, are put through). The odds of being killed by a refugee terrorist? One in 3.6 billion.

“Of the 3,252,493 refugees admitted from 1975 to the end of 2015, 20 were terrorists, which amounted to 0.00062 percent of the total,” Nowrasteh writes. “Of the 20, only three were successful in their attacks, killing a total of three people.”

In 2014, there was a mini panic — fueled largely by elected Republicans — about ISIS sneaking into the United States through the Mexican border. Nowrasteh examined that, too, looking to see how many unauthorized immigrants ended up becoming terrorists.

The answer, once again, was almost none.

“Only 10 [unauthorized] immigrants became terrorists, a minuscule 0.000038 percent of the 26.5 million who entered from 1975 through 2015,” he writes. “Only one of those [unauthorized] immigrants, Ahmed Ajaj, actually succeeded in killing an American.”

The data, then, is very clear: There is no evidence, either pre- or post-9/11, that immigration poses a serious terrorist threat to the United States. Yet Trump has enacted draconian restrictions on immigration in the name of preventing terrorism anyway.

Correction: This piece initially said the percent of deaths from 9/11, out of the total deaths from immigrant-executed terrorist attacks, was 93.7 percent. The correct figure is 98.6.