Terrorism deaths by ideology: Is Charlottesville an anomaly?

Findings
Terrorists have murdered 3,342 people on U.S. soil from 1992 through 12 August 2017. Islamists committed 92 percent of all those murders and are, far and away, the deadliest group of terrorists by ideology. The 9/11 attacks accounted for 2,983 of the 3,085 Islamist-inspired terrorist deaths—an overwhelming 97 percent. The chance of being murdered in a terrorist attack committed by an Islamist during this period was about 1 in 2.5 million per year. 

Nationalist and Right Wing terrorists are the second deadliest group of terrorists by ideology and account for 219 murders and 6.6 percent of all terrorist deaths. The chance of being murdered in a Nationalist or Right Wing terrorist attack was 1 in 33 million per year. The 1995 Oklahoma City bombing, the second deadliest terrorist attack in U.S. history after 9/11, killed 168 people and accounted for 77 percent of the murders committed by Nationalist and Right Wing terrorists. Left Wing terrorists killed only 23 people in terrorist attacks during this time but 13 since the beginning of 2016. Nationalist and Right Wing terrorists have only killed 5 since then, including Charlottesville. Meanwhile, the annual chance of being murdered by a Left Wing terrorist was about 1 in 330 million per year. Regardless of the recent upswing in deaths from Left Wing terrorism since 2016, Nationalist and Right Wing terrorists have killed about 10 times as many people since 1992. Terrorists with unknown or other motivations were the least deadly. 

The distribution of injuries committed by terrorists is similarly ideologically skewed. Attacks committed by Islamists are responsible for almost 94 percent of the 17,471 injuries during the entire period. Nationalist and Right Wing terrorists are responsible for 998 injuries, or 5.7 percent of the total. Left Wing terrorists are responsible for 46 injuries, or 0.26 percent of the total. Nationalist and Right Wing terrorists injured about 22 times as many people in terrorist attacks as Left Wingers did during this time. 

Injuries is a less clear category of damage that can range from a few scratches to amputations or brain damage. The annual chance of being injured in a terrorist attack does not reveal as much as your annual chance of being injured but I included it anyway.

The risk of being killed or injured in a terrorist attack on U.S. soil is small. However, a comparison to other intentional harms can put the risk in perspective. The chance of being murdered in a non-terrorist homicide from 1992 through 2017 was about 1 in 17,000 a year, which is about 133 times as great as being killed by terrorism during that time.

Islamism is an ideology created overseas, while much of the ideology that inspires Nationalist, Right Wing, and Left Wing terrorism is home grown or it has been here for so long that it might as well be.

Conclusion
Islamist terrorists are the deadliest since 1992. They killed about 14 times as many people as Nationalist and Right Wing terrorists who, in turn, killed about 10 times as many people as Left Wing terrorists did. The deadliness of terrorists by ideology has changed over time and will continue to do so. Charlottesville was a tragedy and the person responsible should be tried and, if convicted, punished to the fullest extent possible under the law. However, it is important to realize that the actual scale and scope of the recent terrorist threat differs significantly by ideology even though the annual chance of being murdered in such an attack is still small.

Terrorism deaths and injuries by ideology: Excluding the outlier attacks
My recent blog post on the deaths and injuries caused by terrorists according to their motivating ideologies sheds some light on how frequent attacks like Charlottesville occur. I found that there were 3,342 total murders on U.S. soil caused by terrorists from 1992 through 12 August 2017. Of those, Islamists were responsible for 92 percent, Nationalist and Right Wing terrorists for about 7 percent, and Left Wing terrorists for less than one percent. The most common query after reading my post was: “What happens if you exclude deaths from the outlier attacks of 9/11 and the Oklahoma City bombing?” 

I originally did not exclude the deaths in these outlier attacks in my first post because I merely sought to describe who was killed and by whom. In response to that common question, I decided to post the results that exclude the outlier 9/11 and Oklahoma City attacks. Doing so changes the ratio of murders by ideology but it does not change which terrorism-inspired ideologies are the deadliest.

I subtracted the 2,983 deaths and 14,842 injuries caused by Islamist terrorists on 9/11 and the 168 deaths and 650 injuries caused by a Nationalist/Right Wing terrorist in the Oklahoma City bombing. Excluding the outliers reduces the total number of deaths by 94 percent from 3,342 to 191. The number of injuries also falls, by 91 percent. Just two attacks account for nearly all of the deaths and injuries, though 9/11 was the bigger contributor. After removing the outlier deaths and injuries, Islamist-inspired terrorists are responsible for 53 percent of the murders and 77 percent of the injuries. That is a decline from my original post where I included 9/11 and found that Islamists are responsible for 92 percent of deaths and 94 percent of injuries. The relative percentage of murders committed by Nationalist and Right Wing terrorists rises from about 7 percent in my original post to 27 percent when the 9/11 and the Oklahoma City attacks are excluded. The deaths by Left Wing terrorists also grow in importance from less than 1 percent to 8 percent. 

If we exclude the outliers, we see that Islamist terrorists killed 102 people while Nationalists and Right Wing terrorists killed 51. The number killed by Left Wing and Unknown/Other terrorists remained unchanged at 23 and 15, respectively. The injuries also drop dramatically.

This post – and the subsequent post — were originally published by the Cato Institute.