FIGURE II-7 Gun and nongun homicide rates per 100,000 persons, 1968-2000, New York City.
SOURCE: Fagan et al., 2007; used by permission.

with regard to Hamas (Crenshaw, 2000), one would observe a time-lagged correlation between measures of communal support and measures of militant action, with attacks increasing as support for those attacks increased. We also speculated that major historical events, such as Ariel Sharon’s stepping onto the Temple Mount and the construction of the security wall, would perturb the relationship between communal support and attacks. The data were more complex. While some upswings or downswings in attacks seemed explicable by reference to communal support or major historical/policy changes, an asymmetric quasi-sigmoid curve emerged that could not be accounted for entirely by these factors (see Figure II-8).

Comparing Figures II-7 and II-8, and acknowledging the major differences in the types of aggression and the methodology of data acquisition, one is at least tempted to consider the possibility that (a) contagion-like dissemination of aggressive behaviors may help to explain otherwise mysterious fluctuations, and (b) the early prediction of asymmetric quasi-sigmoid trajectories in the occurrence of such phenomena seems defensible.

Obviously, if there exists an asymmetric sigmoidal trend in the occurrence of communal violence of widely disparate types, that pattern of variation-with-time has a cause. For both theoretical reasons and because of our Palestinian data, I propose a hybrid model of the contagion hypothesis.

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