The Implication of Terrorism’s Extremely Low Base Rate

A robust empirical finding is that global neojihadi terrorism is extremely rare in Western countries compared to other kinds of violence. Its base rate in the West is about 3 new global neojihadis per 100 million people per year. Bayesian conditional probability shows that this extremely low base rate ensures that any attempt to detect a potential global neojihadi on the basis of imperfectly specific indicators (conditions) will generate a large number of false positives. This finding has practical implications for a preventive counterterrorism strategy based on detection of potential global neojihadi terrorists using these indicators derived from counterterrorism research. Detection instruments based on them produce many false positives, namely overt sympathizers, who, absent state agents’ entrapment, never cross the line to political crime and violence. The state pursuit of false positives not only diverts scarce resources from targeting true threats but also results in unfair harassment, persecution, and even prosecution of these false positives. This paper suggests that, as scholars whose work helps craft these indicators, we have the moral duty to teach state practitioners about this relatively neglected implication of the extremely low base rate of global neojihadi terrorism.