How Concentrated Are Police on Crime? a Spatiotemporal Analysis of the Concentration of Police Presence and Crime

Abstract

What were the spatiotemporal patterns of police patrol in a major European city across the pre-COVID year of 2019, how did these patterns change over time, and to what extent did the concentrations of patrol correspond to concentrations of crimes? We analyzed more than 77 million GPS signals from 130 police patrol cars showing where and when police patrols were present in police districts and street segments. We also plotted location, time and days of the week of the locations, and times of more than 50,000 recorded crimes. We calculated concentration ratios within both crimes and patrols relative to their distributions in time and space. We then compared the concentration ratios for crime to the concentration ratios for patrols. We concluded the analysis by comparing the extent to which concentrations of crime and patrol locations and times were overlapping. We found that police patrols, much like crime, were concentrated on a small proportion of street segments. Yet spatiotemporal police presence is unrelated to local levels of crime and crime concentration. Relative to temporal crime concentrations, police patrols were substantially under-concentrated from 1500 to 0100 h, all day on Fridays, and the entire months of June, July, August, and December. There was very little overlap in patrol concentrations with crime concentrations. After three decades of research showing crime prevention benefits of patrol concentrations on micro-level crime concentrations, police in one European city concentrate patrol presence at locations, times, days, and months where crime is not concentrated. Whether this conclusion can be reached in other cities will depend on replications of this study, both in Europe and other continents.