Inverse Distance Variations for the Flow of Crime in Urban Areas

This paper reports the results of fitting migration rules based on gravity models and the theory of intervening opportunities to the of crimes among urban locations. Crime, like other phenomena of demographic flow, is shown to be subject to the general class of inverse distance variations formulated as gravity laws. While the theory of intervening opportunities fares poorly in comparison to models incorporating a measure of distance, the best fit achieved empirically is based on a composite gravity rule that includes a term roughly equivalent to Stouffer's concept of opportunities. A separate analysis of the of property crimes failed to improve the fit of models otherwise successful in predicting the of all crimes. This paper reports preliminary results of work recently undertaken to model the of crime in urban areas. Our interest is in the migration of offenders from their places of residence to the locations where they commit their crimes. 1 The flow of crime, as we define it here, refers to the several streams of criminal migration among urban locations. The surprising absence of past research on this phenomenon, no doubt partly due until recently to the unavailability of suitably comprehensive data, has meant that many questions raised by the mobility of crime for students of urban ecology have gone unanswered. Though many of these questions derive from obvious practical and theoretical interests, our focus here might best be described as demographic. Our purpose is not to inquire into the social psychology of criminal migration, nor into the specific social and economic matters that influence particular decisions to commit crimes at given locations within urban areas, but instead to ask whether the gross demographic phenomenon itself-the sheer of crime within the city-conforms to known rules describing other forms of demographic gravitation. The most successful models employed in social research to study demographic flows are based on the physical laws of gravity. By analogy to the rules of Newtonian mechanics, gravity models postulate a gross force of attraction operating along a straight line between two points. The magnitude of this attraction, as seen in the exchange of population, is directly proportional to the product of their respective *The author wishes to acknowledge the generous advice and collegiality of Poduri S. R. S. Rao, and the helpful comments of Lois Horwitz, Klaus Roghmann, R. Danforth Ross, Barbara Sobieszek, and Paul Westcott. This research was supported under Grant 74 NI-02-0002, from the National Institute of Law Enforcement and Criminal Justice of the Law Enforcement Assistance Administration, United States Department of Justice. Statements or conclusions contained in this paper do not necessarily indicate the concurrence of the Institute.