In 1994, the New York City Police Department adopted a law enforcement crime fighting strategy known as COMPSTAT (COMPuter STATistics). COMPSTAT uses Geographic Information Systems (GIS) to map the locations of where crimes occur, identify “hotspots”, and map problem areas. COMPSTAT has amassed a wealth of historical crime data. Mathematicians have designed and developed algorithms that run against the historical data to predict future crimes for police departments. This is known as predictive policing. Predictive policing has led to a drop in burglaries, automobile thefts, and other crimes in some cities.