Terrorism undoubtedly poses a grave threat to the security of open societies. Conventional wisdom holds that terrorists also hold the power to inflict grave harm upon modern economies. Many cite the significant economic consequences of the September 11 attacks as evidence of our economic vulnerability. What were the actualeconomic consequences of September 11, the largest terror attack in history? Are modern economies in fact highly vulnerable to terrorist disruption? What future risks do different types of terrorist attacks pose for Western economies?