Extreme Vetting of Immigrants: Estimating Terrorism Vetting Failures

Featuring David Bier

President Donald Trump has promised to implement “extreme vetting” of immigrants and foreign travelers, asserting that widespread vetting failures had allowed many terrorists to enter the United States. This policy analysis provides the first estimate of the number of terrorism vetting failures, both before and after the vetting enhancements implemented in response to the September 11, 2001, attacks. Vetting failures are rare and have become much rarer since 9/11.