Abstract: The only publicly-available information on the geographical distribution of crime in New Zealand is offence statistics for police administrative units. We investigate whether existing data can be used to construct geographical crime statistics that correspond to regional councils, territorial authorities, and urban areas.
We build experimental output geographies from police stations, the smallest administrative unit for which there are long time series of offence statistics. We develop three rules for assigning police stations to the new geographies: one based on population, one based on land area, and one based on both. We assess the performance of these rules by calculating the proportion of national land area and population that is misclassified, and the number of target units that do not receive at least one police station. We also look at whether regional statistics on serious assaults are sensitive to the choice of allocation rule.
The new output geographies approximate the target geographies well. For instance, our preferred rule assigns 96 percent of the national population to the correct territorial authority. Moreover, a case study of serious assaults suggests that most regional crime statistics are not sensitive to the choice of rule.
The new output geographies perform sufficiently well that they could, if required, be used to produce regional crime statistics.