May 8, 2019 5:03PM

New Research on Immigration, Terrorism, and Ideology

Yesterday, Cato released my latest policy analysis entitled “Terrorists by Immigration Status and Nationality: A Risk Analysis, 1975–2017.” Much of it is an update and expansion of my original policy analysis on this topic from 2016. I added two more years of data, estimates of the number of people injured, and a handful of non‐​deadly foreign‐​born terrorists whom I had failed to include in my original paper. The annual risk of being murdered in an attack committed by a foreign‐​born terrorist by visa category is very similar to my original study as there were only a handful of victims from attacks perpetrated by foreign‐​born terrorists in 2016 and 2017. 

Overall, the chance of being murdered by a foreign‐​born terrorist was about 1 in 3.8 million per year during the 43‐​year period in which 3,037 people were murdered. Foreign‐​born terrorists who entered on tourist visas were the most deadly, responsible for over 96 percent of those deaths – largely because 18 out of the 19 9/11 hijackers entered on tourist visas. 

The changes to this analysis mentioned above are small, but there are two major additions that you should pay attention to. The first is that I included all 788 native‐​born terrorists during this time by applying the same exclusion criteria that I applied to foreign‐​born terrorists. It took years and reading tens of thousands of pages of government documents, news stories, dissertations, reports by non‐​profits, and more biographies of sketchy people than I care to remember. Just for the record, there are a lot of Nazis who have been killed in shootouts with the police but most of them are not terrorists. All 788 native‐​born terrorists are listed in the appendix. If you think I missed somebody or included somebody I shouldn’t have, please let me know. 

The second major addition to the updated policy analysis is that I categorized all terrorists by the ideology that motivated them. In order of the size of their body counts, the ideologies are Islamism, Right, White Supremacy, Left, Black Nationalism, Anti‐​abortion, Unknown/​Other, Foreign Nationalism (Armenian terrorists targeting Turks in revenge for the genocide), Separatists (Puerto Rican independence, Texas secessionists, etc.), Anti‐​specific Religion (anti‐​Semitic shooters, etc.), Political Assassination, and Religious (non‐​Islamist).

I decided to separate White Supremacists, Right, and Anti‐​Abortion terrorists because they are all different ideologies. True, they would mostly all label themselves as right‐​wing, but this enhanced level of detail conveys a deeper understanding of American terrorism. Most Black Nationalists, Left, and Separatist terrorists would also label themselves as left‐​wing, but I made the same judgment call and separated them into their sub‐​ideologies for the same reason. Similarly, separating Islamist terrorists into Sunnis or Shiites wouldn’t add much clarity so I didn’t do that. 

After the Christchurch mosque terrorist attack in New Zealand in March, many people wrote that right‐​wing or white‐​supremacist terrorism is on the rise. While my updated report only covers the United States through 2017 and most of those writers were discussing the issue globally, my research can provide some evidence of whether this is true inside of the United States.

Over the entire 43‐​year period, the deadliness of Islamist terrorism dwarfs Right, White Supremacy, and Anti‐​abortion terrorism by factors of 16, 40, and 239, respectively. The picture changes somewhat more recently as Islamists are responsible for 58 percent of all murders in terrorist attacks since 9/11, White Supremacists are responsible for 17 percent, Right terrorists for 10 percent, Left terrorists for 8 percent, and then the numbers get tiny. Islamism is still the deadliest terrorist ideology in the post‐​9/​11 world relative to Right, White Supremacy, and Anti‐​abortion, but by smaller factors of 6, 3, and 27, respectively. Those numbers may well have diverged in 2018 and 2019, but I doubt they’ve changed enough to alter the general pattern.

Since 9/11, 184 people have been murdered by 378 terrorists in attacks on U.S. soil. Of those 378 attackers, 62 managed to murder at least one person in an attack. That means that only 16.4 percent of attackers succeeded in murdering somebody. On this count, Right and White Supremacist terrorists are the most likely to succeed in murdering at least one person in their attacks at 28 and 22 percent, respectively. Islamist terrorists have been less successful, with only 9 percent of them succeeding in murdering at least one person. However, because there were so many Islamist terrorists and each one of them was deadlier on average, that ideology still inspires the deadliest terrorists. It’s a bit premature to write the epitaph for Islamist terrorism in the United States. 

The main lesson from this report is that there are very few terrorists of any ideology or origin and even fewer who manage to murder Americans. The 3,518 total murder victims of terrorism killed by foreign‐​born, native‐​born, and unknown terrorists from 1975–2017 account for only about 0.4 percent of the roughly 800,000 homicides during that time. The ideology, frequency, deadliness, and origins of terrorists are fascinating but these numbers are so small that it is difficult to tease out any trend, let alone to be overwhelmed by fear.