Counting crimes: the importance of understanding crime concentration for the design and evaluation of crime reduction strategies

Crime statistics are most frequently concerned with the incidence of crime (usually quoted as a rate per population), occasionally statistics are concerned with prevalence (number or proportion of victims within the population) but the concentration of crime (number of crimes per victim) is rarely quoted. This paper aims to demonstrate the importance of all three indicators of crime, prevalence, concentration and incidence, for understanding crime levels through an analysis of self-reported victimisation data from 39 high-crime areas. The analysis illustrates that areas can have high crime either as a result of high levels of victimisation (prevalence), high numbers of crimes per victim (concentration) or a combination of both. These underlying dimensions of a crime problem must be understood in order to select the most suitable crime prevention interventions, and to target them appropriately.