When it comes to gun violence, it’s tough to beat street gangs. They have made a sport of it. But the spooky question has been, “How much gun violence is gang violence?” Thanks to a little triangulation on our part, we think it is amplissimum. Major Take-aways Gangs likely constitute 85% of firearm homicides in the US. There is a close correlation between metropolitan gang-age homicides and estimates of gang populations by degrees of urbanization. The Data Dearth For all the great scorekeeping the FBI does, when it comes to murder, they have understandable gaps. Every year the FBI reports on the circumstances that led to a homicide, in their Expanded Homicide Tables. There are two rows of data that list what police were absolutely certain were gang related murders.