Yesterday, President Trump tweeted that “unknown Middle Easterners are mixed in” with the migrant caravan approaching the U.S. border. Vice President Pence later tried to justify President Trump’s comment by arguing that, “It is inconvincible that there are not people of Middle Eastern descent in a crowd of more than 7,000 people advancing toward our border.” Todd Bensman of the Center for Immigration Studies wrote that “the president was obviously referencing … ‘special interest aliens’ … U.S.-bound migrants moving along well‐​established Latin America smuggling routes from [Muslim] countries.” Perhaps President Trump was referencing special interest aliens but the clear implication is that they are potential terrorists who are using the caravan to sneak into the United States and murder Americans.

The members of the migrant caravan will either apply for asylum at the U.S. border or try to enter illegally. From 1975 through the end of 2017, 9 Americans have been murdered in attacks committed on U.S. soil by 20 foreign‐​born terrorists who entered illegally or as asylees. During that time, the annual chance of being murdered in a terrorist attack committed by an asylum seeker or an illegal immigrant was about 1 in 1.3 billion per year. Those estimates are based on this methodology with updated numbers.

During that time, about 31.3 million illegal immigrants entered the U.S. illegally (most have since emigrated, legalized, or passed away) and about 732 thousand asylum seekers have been admitted. Nine of the 20 terrorists who entered did so as illegal immigrants, meaning that about 1 terrorist entered hidden amongst every 3.48 million illegal immigrants. They killed zero people in domestic terror attacks. The 11 terrorists who entered as asylum seekers murdered 9 people in terrorist attacks or about 1 murder for every 81,000 asylum seekers let in.

Of those 9 terrorists who entered illegally, only 3 did so along the border with Mexico: Shain Duka, Britan Duka, and Eljvir Duka crossed as children with their parents in 1984. They are ethnic Albanians from Macedonia. They were 3 conspirators in the incompetently planned Fort Dix plot that the FBI foiled in 2007, long after they became adults and more than two decades after they entered illegally. There is no evidence that the Fort Dix plot was more than 23 years in the making.

As far as we can tell, virtually all the members of the migrant caravan come from Central America while the asylum‐​seeker and illegal immigrant terrorists who committed or attempted to commit attacks on U.S. soil came from Cuba, Lebanon, Pakistan, Palestine, Canada, Algeria, Somalia, Macedonia, Kyrgyzstan, and Afghanistan. Not a single terrorist in any visa category came from Mexico or Central America during the 43‐​year period.

None of the above estimates are meant to imply that those asylum seekers or illegal immigrants who committed or attempted to commit attacks were terrorists when they entered. Some, like Ramzi Yousef, obviously did enter as terrorists but the Boston Bombers Dzhokhar Tsarnaev and Tamerlan Tsarnaev entered as children too young to be plotting a terrorist attack years later. My colleague David Bier has shown just how rare it is that a foreign‐​born terrorist intends to come to the United States and how infrequently the government fails to stop him or her.

This issue is complicated by the recent statements of Guatemalan president Jimmy Morales, who announced that his government “apprehended close to 100 persons completely involved with terrorists, with ISIS and we have not only detained them within our territory, but they have been deported to their country of origin.” Morales then stated that information about these supposed terrorists (like their names or countries of origin) was classified, which should raise a red flag as governments love to brag about their anti‐​terrorism actions with specifics even when such bragging is unjustified.

Even if we assume that some members of the migrant caravan are Middle Easterners who might pose a higher terrorism risk, that is still no good reason to bar the Central American migrants from applying for asylum. If some Middle Easterners are in this caravan, they too will be able to apply and face the same terrorism vetting procedures that work so well. There is little evidence that there are Middle Easterners in this caravan, even less that there are actual terrorists, and the risk from terrorists crossing the border has been tiny historically. This time could be different, but there is no real evidence to suggest that it is. Whatever problems may arise due to this caravan, the actual threat of terrorism from its members is very small.