Evidence from Prohibition shows that legalizing marijuana and ending the black market may lead to a decline in violence

One of the arguments put forward for the legalization of drugs such as marijuana, is that it will lead to a fall in violence associated with the black market for drugs. But should the two US states who have recently legalized the growth and consumption of marijuana now expect such a fall in violent behavior? Using data from the time of alcohol Prohibition in the 1920s, Emily Owens finds that violent homicides for those in their 20s (the age commonly associated with criminal violence) increased during Prohibition, and then fell once it was repealed, while violent homicides fell for those in their 30s, largely due to less alcohol fuelled violence.