A paper from the National Bureau of Economic Research suggests that between 19-29% of the decline in US murder rates in the 1990s may have been due to the impact of mobile phones on the illegal drug trade.

The theory is that accessible mobile phones allowed the black market trade to be conducted and coordinated privately by phone. Customers could be met at discreet locations rather than trade needing to be plied directly on the street in fixed locations. This reduced street-level turf battles between gangs who funded their activities via drug sales in ways that frequently involved violence, as well as potentially “democratising” the market to allow other types of sellers in.