Transnational dynamics and Islamist terrorism in the West

In most contemporary Islamist terrorist plots in the West, we suspect a transnational component. This study attempts to identify and quantify this component. The author has created a data set of Islamist terrorist attacks, and foiled and failed plots in the West as well as against Western targets outside the West, from 1989 to 2008. From similar findings in studies of left-wing terrorism of the 1960s and 1970s, a contagion effect from terrorism outside the West to inside the West is expected. Using ordinary least squares (OLS) regression, this paper finds a very strong relation between terrorism against Western targets abroad and terrorism in the West, with a 2-year time lag. This relation proves robust even when controlling for the effect of the two Gulf wars and the war in Afghanistan. Surprisingly, no statistically significant effect from these three wars can be identified on the level of terrorism in the West. Instead, the wars apparently had a significant effect on the level of terrorism against Western targets outside the West, thereby possibly indirectly affecting the level of Islamist terrorism in the West.