ABSTRACT
Measuring crime has always been a key priority for criminologists. Early on, scholars realized the utility of “construct[ing] crime occurrence rates on the basis of environmental opportunities specific to each crime” (Boggs, 1965: 899). Such constructions yield valuable information whether crime targets in certain spatial areas are be more exploited than similar targets in other spatial areas, particularly when crime counts are similar and populations at risk differ (Pittman and Handy, 1962; Boggs, 1965). However, calculating these opportunity-based crime occurrence rates meant a deviation from the conventional calculation of crime rates that used the residential population in the spatial unit under analysis as the denominator. As Boggs (1965) states: “[s]ince the number of events, or the numerator, varies with the type of crime, the denominator should likewise vary so that the whole number of exposures to the risk of that specific event is incorporated as the base” (Boggs, 1965: 900). Therefore, if one always uses the residential population in the calculation of crime rates when better measures are available, valuable information is not being incorporated into the analysis. In the 1960s when Boggs put forward her idea, it was clear that using these alternative denominators may result in substantial work and would incur high costs that would have a consequence: most of the information needed to develop an opportunity-based measure was not being collected in common data sources such as the census, such that the developments of opportunity-based crime rates have been few and far between.
