Measurement of Repeat Effects in Chicago's Criminal Social Network

The "near-repeat" effect is a well-known criminological phenomenon in which the occurrence of a crime incident gives rise to a temporary elevation of crime risk within close physical proximity to an initial incident. Adopting a social network perspective, The current study instead defines a "near-repeat" in terms of geodesic distance within a criminal social network, rather than spatial distance. The study divided the arrest data into two sets (violent crimes and other crimes) and, for each set, it compared the distributions of time intervals between repeat incidents to theoretical distributions in which repeat incidents occurred only by chance. The study first considered the case of the same arrestee participating in repeat incidents ("exact repeats") and then extended the analysis to evaluate repeat risks of those arrestees near one another in the social network. Repeat effects were observed that diminished as a function of geodesic distance and time interval, and typical time scales were estimated for repeat crimes in Chicago. (Publisher abstract modified)