The Impact of Category Spanning on the Lethality of Terrorist Organizations

She is widely known as one of the pioneers of ethnic competition theory and does research on armed conflict, ethnic violence, collective action, and social movement organizations. From 22 September to 3 October she will be at the WZB as a guest researcher.

Her paper tests arguments about category spanning and organizational success with data on organizations that engaged in terrorist acts between 1998 and the end of 2005. The core argument is that terrorist organizations that span multiple, dissimilar, and distant ideological categories will be less successful at inflicting harm on civilians, when they are compared to other terrorist organizations whose membership lies squarely within a single or more typical ideological category. We evaluate the effect of category spanning using an instrumental variable method of estimation that also takes into account sources of unobserved heterogeneity. Our ivestigation finds that terrorist organizations with specialist ideologies produce a significantly higher number of fatalities per attack when compared to terrorist organizations that have memberships across categories that reflect atypical combinations and distant ideologies.