On September 13, 2016, the Cato Institute published a Policy Analysis by Nowrasteh on "Terrorism and Immigration: A Risk Analysis." He notes that, "Terrorism is a hazard to human life and material prosperity that should be addressed in a sensible manner whereby the benefits of actions to contain it outweigh the costs. ... [T]he chance of an American perishing in a terrorist attack on U.S. soil that was committed by a foreigner over the 41-year period studied here is 1 in 3.6 million per year. The hazard posed by foreigners who entered on different visa categories varies considerably. For instance, the chance of an American being murdered in a terrorist attack caused by a refugee is 1 in 3.64 billion per year while the chance of being murdered in an attack committed by an illegal immigrant is an astronomical 1 in 10.9 billion per year. By contrast, the chance of being murdered by a tourist on a B visa, the most common tourist visa, is 1 in 3.9 million per year. Any government response to terrorism must take account of the wide range of hazards posed by foreign-born terrorists who entered under various visa categories."
