The study, published in the Journal of Economic Behavior and Organization, was written by a group of economists from the University of Bologna in Italy. It examines crime data from 2013 and 2014, the two-year time span when recreational cannabis was legal in the state of Washington, but illegal in its neighbouring state, Oregon.
‘First-pass evidence is provided that the legalization of the cannabis market across U.S. states is inducing a crime drop,’ write the authors in the study’s abstract. ‘We exploit the staggered legalization of recreational marijuana enacted by the adjacent states Washington (end of 2012) and Oregon (end of 2014).’
By comparing crime statistics and drug consumption data from counties along the border in each state, they determined that legalization led to a ‘significant reduction in rapes and property crimes’ in Washington in the two years following legalization, relative to both counties in Oregon during the same time period, and counties in Washington between 2010 and 2012.
According to the authors of the study, the number of reported rapes was reduced by between 15 and 30 percent, while thefts were reduced by 10 to 20 percent.
While the consumption of cannabis did increase in the state of Washington after legalization (as researchers likely expected), they found that the consumption of other drugs including alcohol was reduced, as were incidents of binge drinking.
Though the authors of the study were obviously unable to determine exactly why crime rates were reduced after legalization, they do offer explanations as to what may have contributed to the overall reduction.
They cite the psychotropic effects of cannabis (producing ‘a state of relaxation and euphoria’) as something that may ‘[reduce] the likelihood of engaging in violent activities’, while also noting that people were probably substituting cannabis for ‘violence-inducing substances such as alcohol, cocaine, and amphetamines’.
Looking at the effects of legalization on the police, they suggest that a reallocation of resources away from cannabis-focused crimes to other offences may have also played a role. As for the black market, authors note that legalization may have reduced the role of criminals operating in the business.
While more research on the subject is needed, some previous studies also suggest that when you increase cannabis access in an area (or, as in this study, remove it), crime rates are affected in an inverse way.