A Generalized Aggregation-Disintegration Model for the Frequency of Severe Terrorist Attacks

The authors present and analyze a model of the frequency of severe terrorist attacks, which generalizes the recently proposed model of Johnson et al. This model, which is based on the notion of self-organized criticality and which describes how terrorist cells might aggregate and disintegrate over time, predicts that the distribution of attack severities should follow a power-law form with an exponent of alpha = 5/2. This prediction is in good agreement with current empirical estimates for terrorist attacks worldwide, which give (alpha) over cap = 2.4 +/- 0.2 and which the authors show is independent of certain details of the model. The authors close by discussing the utility of this model for understanding terrorism and the behavior of terrorist organizations and mention several productive ways it could be extended mathematically or tested empirically.