Terrorism and Immigration: A Risk Analysis, 1975–2023

By Alex NowrAsteh

  Terrorism is a hazard to human life and material prosperity that should be addressed in a sensible manner whereby the benefits of government actions taken to contain it outweigh the costs. Whether policies are sensible depends on the risks that terrorism poses, the harms that terrorism inflicts, and the costs of anti-terrorism policies. This risk analysis of foreign-born terrorism is a crucial step in evaluating anti-terrorism policies related to immigration. A total of 230 foreign-born terrorists were responsible for 3,046 murders on US soil from 1975 through the end of 2023. The chance of a person perishing in a terrorist attack committed by a foreigner on US soil over that 49-year period was about 1 in 4.5 million per year. The hazard posed by foreigners who entered in different ways varies considerably. For instance, the annual chance of being murdered in an  attack committed by an illegal immigrant was zero. The federal government has an important role in screening foreigners who enter the United States and excluding those who pose a threat to the national security, safety, or health of Americans, as foreign-born terrorists explicitly do. This policy analysis does not make predictions about foreign-born terrorism on US soil; it merely analyzes the past risk posed by foreign-born terrorists on American soil. The past is the only source of data and information available about foreign-born terrorists on US soil, but foreign-born-terrorist trends could change, and there is no guarantee that past trends will continue. Still, the data and information in this focused terrorism risk analysis can aid in the efficient allocation of scarce government resources to best counter the small threat of foreign-born terrorists.  

   Policy Analysis no. 972

Washington, DC: Cato Institute, 2024.  28p.