Cato Paper Highlights Marijuana Legalization’s Ho-Hum Impact in Colorado

In a new Cato Institute
working paper, Harvard economist Jeffrey Miron finds little
evidence that the loosening of marijuana prohibition in Colorado
has had a noticeable impact on adult or underage cannabis
consumption, traffic accidents, violent crime, drug treatment
admissions, emergency room visits, drug-related deaths, educational
outcomes, or economic growth. Miron, Cato’s director of economic
studies, considers trends in these indicators before and after
2009, when the medical marijuana industry took off due to
regulatory developments that made it more secure, and 2012, when
voters approved Amendment 64, which legalized marijuana for
recreational use. Generally speaking, there is no significant
change in these trends after those policy shifts. Here, for
example, is how violent crime rates in Denver look:

In this case, data are available for the months following the
beginning of legal recreational sales last January. Looking at
murders, aggravated assaults, robberies, and burglaries, Miron
concludes that “no measure indicates a significant change in crime
after medical marijuana commercialization, legalization adoption,
or full legalization implementation.”

I have discussed some of these trends here, including
crime,
underage use,
traffic fatalties, and
drug treatment admissions. Miron also looks at several
educational outcomes: school suspensions, standardized test scores,
and high school graduation and dropout rates. Changes in marijuana
policy do not seem to have had an impact on these outcomes, with
the exception of drug-related suspensions, which rose after
the commercialization of medical marijuana in 2009 and again after
the legalization of recreational marijuana in 2012, even as total
suspensions declined.

Miron not only finds little evidence of negative fallout from
changes in Colorado’s marijuana policies; he also finds little
evidence that legalization has had a positive impact on the
measures he considers. It does not seem to have slowed or
accelerated economic growth, for example, or to have increased or
reduced traffic accidents. Looking at “fatal car crashes,
fatalities in car crashes, alcohol-related fatal car crashes, and
fatalities in alcohol-related car crashes,” Miron finds that “no
measure exhibits a substantial change at the time of marijuana
policy changes.”

Miron concludes that “strong claims about Colorado’s
legalization, whether by advocates or opponents, are so far devoid
of empirical support.” As far as broad legalization goes, of
course, it is still early going in Colorado, and negative or
positive effects may become apparent in the coming years. Miron
plans to keep an eye on trends in Colorado and other states that
legalize marijuana, ultimately comparing them to data from other
states to get a clearer idea of what happens after prohibition
ends.