Introduction to hot spot rate mapping

Certain crime and disorder incident types require the need to consider the distribution of an underlying population for identifying areas to focus resources. A good example is residential burglary. A hotspot map of burglary by volume of incidents may reveal nothing more than the areas of high housing density.

To take account of these uneven distributions of underlying populations, the use of suitable variables as denominators for generating rates are required. Commonly, the most reliable denominator of this type is that which is collected by the Census. For example, residential household data is available at enumeration district level and can be linked with enumeration district residential burglary counts to produce an area rate. These rate values can then be thematically mapped by these enumeration districts.

Care needs to be taken in choosing suitable denominators to calculate crime rates and how these are then interpreted. This is because several that are commonly used can mislead. For example, robbery rates per 1000 population can often greatly exaggerate the crime problem in areas of small residential populations but which have high daytime populations. This is often the case in town centres.