https://www.nber.org/papers/w25883#fromrss
Cell phones may have undercut turf-based street dealing, thus undermining drug-dealing profits of street gangs, entities known to engage in violent crime. Studying county-level data for the years 1970-2009 we find that the expansion of cellular phone service (as proxied by antenna-structure density) lowered homicide rates in the 1990s.
