Gang activity and overall levels of crime: A new mapping tool for defining areas of gang activity using police records

In this note, a new method for defining gang activity areas based upon police records is illustrated using the Chicago Police Department's 1996 incident files. This method is based upon standard geographic techniques and uses a uniform grid that divides the city into 150-m squares. It is shown that this technique may be useful both in describing gang activity areas and in describing the spatial distribution of crime in large cities. A strong relationship is found between the number of gangs that are active in an area and the general level of criminal activity.