This post was updated to include all convictions or attacks through October 31, 2017.

President Trump’s executive order attempted to temporarily ban all refugees and all travelers or immigrants from six African and Middle Eastern countries due to a concern over widespread vetting failures. The purpose of the temporary ban was to give the administration time to “improve the screening and vetting protocols and procedures.” The order grounded this concern in one fact:

Recent history shows that some of those who have entered the United States through our immigration system have proved to be threats to our national security. Since 2001, hundreds of persons born abroad have been convicted of terrorism-related crimes in the United States.

These statements contain five clear implications: 1) that these “hundreds of persons born abroad” committed acts of terrorism in the United States; 2) that they came to the United States “through our immigration system,” 3) that they entered since 2001, 4) that better “screening and vetting protocols” could have prevented their entry, and 5) these offenders pose a significant threat to Americans. Each one of these implications is false. Here are the facts:

1) Not “hundreds of persons” committing terrorism in the United States: Only 55 percent of people convicted of “terrorism-related” offenses according to the federal government are, in fact, convicted of involvement in terrorism.

2) Not “hundreds” through our immigration system: Less than 200 foreigners convicted of or killed during terrorism offenses since 9/11 entered “through our immigration system.”

3) Not “hundreds” entering since 9/11: Only 35 foreigners convicted of or killed during terrorism offenses since 9/11 entered “through our immigration system” since 2001.

4) Not “hundreds” slipping through “screening” since 9/11: Only 17 likely radicalized prior to entry.

5) Not a significant threat: No refugee nor any national of the banned countries has successfully carried out a deadly terrorist attack in over four decades.

In the aftermath of the world’s worst terrorist attack on September 11, 2001, the U.S. government rapidly responded with much stricter vetting for foreign visitors, immigrants, and refugees. It created new terrorist watch lists, required biometric verification of identities, instituted mandatory visa interviews, hired thousands of new consular officers, improved inter-agency intelligence sharing, and much else. America’s pre‑9/​11 visa vetting system has almost nothing in common with today’s system. For this reason, it is appropriate to begin the analysis of immigration vetting failures with 9/11.

The government’s terrorism-“related” definition inflates the number of terrorism convictions

The executive order does not reveal the source for the claim that “hundreds of persons born abroad have been convicted of terrorism-related crimes,” but the National Security Division (NSD) of the Department of Justice (DOJ) has published a list of 627 unsealed “terrorism-related convictions” from October 2001 to December 2015. Of this list, however, nearly half—45 percent—were not convicted of a terrorism offense. NSD includes them because the prosecution began with terrorism investigation, even if it did not end with a terrorism conviction. Non-terrorism convictions include mainly false statements to investigators, ID fraud, immigration violations, and drug offenses. Other “terrorism-related” offenses include child pornography, social security fraud, and stealing truckloads of cereal.

Because the NSD list is both overbroad, incomplete, and not fully up-to-date, I also reviewed all terrorism offenders whose convictions were publicized on the DOJ website since 2015 as well as those included in George Washington University’s Program on Extremism (GW) or in New America Foundation’s International Security Program (NAF). NAF includes offenders who lived in the United States for a period before being killed both in the United States and abroad. I created a combined list of NSD, DOJ, GW, and NAF that includes only those convicted of or killed during terrorism offenses. I used court filings and news reports to identify the dates and places of birth and the years of entry for each of them.

In three cases, I was unable to nail down exact entry years, but I was able to obtain some information about their dates of entry. Sixto Ramiro Garcia and Miguel Santana, either naturalized or attempted to naturalize, so legally, they must have each lived at least five years in the United States before they committed to their offenses. Abror Habibov obtained a permanent Social Security Number in June or July 2006, but he had lived in the United States for sometime prior to that, so he likely entered in 2005 or earlier.

Many foreign-born terrorism offenders did not go “through the immigration system”

Of the actual terrorism offenders, nearly 60 percent were either born in the United States or brought into the country by U.S. law enforcement for prosecution or arrest, leaving 199 other foreign-born terrorism offenders who entered “through the immigration system” at some point. Of these, however, only 35 entered through the system after 9/11, again far fewer than hundreds.

Finally, these 35 were not all vetting failures, either. To begin with, 13 entered as juveniles, including eight who entered at 15-years-old or younger (Abdul Artan’s exact age is uncertain, so I included him as an adult). Six of the juveniles converted from Christianity to extremist Islam. Focusing solely on the adults, the government determined that radicalization occurred prior to entry in just 11 cases. In another six cases, it is uncertain whether radicalization occurred prior to entry. Thus, if we assume all six of the other uncertain ones radicalized prior to entry, there were at most 17 “vetting failures” since 9/11—not hundreds.

Very few terrorism vetting failures were from banned countries

The 35 terrorism offenders came from 21 different countries. Notably, it includes eight individuals from non-majority Muslim countries. Of the banned countries—Iran, Libya, Syria, Somalia, Sudan, and Yemen—only three are represented on the list. The 17 vetting failures came from 12 countries. Only eight of them actually attempted to carry out an attack, as opposed to aiding a terrorist group abroad. No single country had more than three vetting failures. Of the banned countries, only Sudan and Somalia had a vetting failure.

Terrorism vetting failures from banned countries caused zero deaths since 9/11

Vetting failures from refugees or the six banned countries represent a tiny portion of the terrorism offenders since 9/11—to be precise, less than 2 percent. More importantly, these offenders caused no deaths. Refugees and nationals of these countries simply have not successfully killed anyone in the United States in the last four decades. In fact, only 14 of the 35 terrorism offenders were involved in a plot to kill anyone in the United States—the others were mainly either going overseas to join a terrorist organization or sending money to them. Among the 17 vetting failures, more than half (eight) were not attempting to kill anyone in the U.S. Only one did: Tashfeen Malik, a Pakistani woman who immigrated using a family-based nonimmigrant visa (fiancé K visa).

These facts contract the claims of the administration that vetting failures are widespread, and that a total rewrite of the system is necessary. My colleague has previously noted that the risk of foreign-born terrorism is miniscule: just a 1 in 3.6 million chance of dying in a terrorist attack on U.S. soil per year. The risk from a post‑9/​11 vetting failure is more than a hundred times less.

Table 1: Foreign Terrorism Offenders Killed or Convicted Who Entered Through the Immigration System After 9/11

Sources: Department of Justice, National Security Division, George Washington University, New America Foundation

Table 2: Foreign Terrorism Offenders Killed or Convicted Who Entered Through the Immigration System or Illegally After 9/11 by Country

Sources: See Table 1

Table 3: Foreign Terrorism Offenders Killed or Convicted After 9/11 Who Entered Through the Immigration System As Adults

*Post was updated 3/13/2018 to reflect that although Ahmed Mohamed was convicted of material support—rather than a plot to attack the United States—government officials at sentencing stated that they believed he was intending to attack targets in the United States. It was also updated to reflect that while he was born in Kuwait, he was a national of Egypt.

Table 4: Foreign Terrorism Offenders Killed or Convicted After 9/11 Who Entered Through the Immigration System As Juveniles

Sources: See Table 1
*Converted to Islam, **Confirmed through his attorney.

Update 11/13/2017: This list was updated to remove two individuals: 1) Antonio Martinez who, although born abroad, was a U.S. citizen at birth by virtue of his mother’s U.S. citizenship. Sami Samir Hassoun who, while he received permanent residency in 2008, had originally entered the United States as a tourist at the age of 12 in 2000, living in Illinois. These changes reduced the number of post‑9/​11 entries by two and eliminate one vetting failure. It also changes Akhror Saidakhmetov to an asylee and corrects his age at entry to 16. Although this source describes him as entering illegally, other government documents list him as entering as a derivative asylee who became a legal permanent resident. It also updates the number of offenders through the end of October, adding two. During this time, there was only one terrorism conviction of a foreigner who entered after 9/11, Abror Habibov, but I also added Sayfullo Saipov, the New York City terrorist because he admitted to the crime and because he killed people.