Waves of Global TerrorismTerrorism is a persistent form of political violence, but it appears intermittently, afflicting certain places in certain eras while others remain unscathed. Since the late nineteenth century, it has risen and fallen in recurrent generation long spasms in which hundreds of short lived groups wreak havoc. Why have past outbreaks of terror tended to come in waves, and how does this pattern shed light on future threats? David C. Rapoport, a preeminent