The “Hottest” Part of a Hotspot: Comments on “The Utility of Hotspot Mapping for Predicting Spatial Patterns of Crime”
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The recent article by Chainey et al. (2008) in the Security Journal made an important contribution to the analysis of crime hotspots by developing a criterion for comparing methods that identify hotspots. However, the methodology they adopted to compare several specific hotspot techniques was limited and, consequently, raised doubts about the conclusions they drew.
In their paper, they developed a measure called the Prediction Accuracy Index(PAI), which is the ratio of the density of crimes in a hotspot relative to the density of crimes in the general study area. The index is applied to the next time period; that is, the hotspots identified in one time period are applied to the crimes occurring in the next time period. This measure is a good criterion for comparing different hotspot techniques. A hotspot method that has a higher PAI has a higher ratio of events per square unit of area than another method with a lower PAI. In other words, a method with a higher PAI is relatively...
I would like to thank Dr. Alan Robertson of the Houston Police Department for help in defining several of the parameters used in the analysis.
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