Our analysis suggests not that gangs cause violence, but that violence causes gangs. In other words, gangs form in response to government's failure to protect youths against violence. The surprising implication of our insight is that efforts to reduce gang activity could actually increase violent crime.
This is from the September Feature Article on Econlib titled "More Gangs, Less Crime," by West Virginia University economics professor Russell Sobel.
I live in a city near Salinas. Salinas has a substantial gang membership. The local government plus the state and federal government are going after gangs in Salinas. But it's not clear from the news reports whether they're going after gangs per se or after crime that gangs participate in. To the extent the various police are going after gangs per se, it will be interesting to see whether crime increases.