Here's what the DPA report found:
1. Teen marijuana use is unchanged.
In both Colorado and Washington, state surveys have shown no significant change in marijuana use among teens since voters passed legalization measures.
Experts also point out that the official state survey, which uses a much larger sample size than the federal survey, indicates that Colorado teens are middle-of-the-pack on marijuana use compared to teens in the rest of the nation.
“Preliminary data show that the legalization of marijuana has had little to no impact on the overall rate of youth use of marijuana,” the DPA report concludes.
2. Marijuana arrests are way down — but racial disparities remain.
“Arrests in all states and Washington, D.C. for the possession, cultivation and distribution of marijuana have plummeted since voters legalized the adult use of marijuana,” the DPA finds, citing official state and municipal numbers. The reduction in arrests is “saving those jurisdictions millions of dollars and preventing the criminalization of thousands of people.”
“By no longer arresting and prosecuting possession and other low-level marijuana offenses, states are saving hundreds of millions of dollars,” the Drug Policy Alliance writes, citing the $200 million spent on marijuana enforcement in Washington state between 2000 and 2010.
Still, the DPA notes that disparities in marijuana arrest rates between black and white citizens remain, even after legalization: “While legalization substantially reduces the total number of blacks and Latinos arrested for marijuana offenses, it does not eliminate the forces that contributed to the disparity in the first place.”
3. Marijuana legalization appears to have had little impact on traffic fatalities.
“In Colorado and Washington the post-legalization traffic fatality rate has remained statistically consistent with pre-legalization levels, is lower in each state than it was a decade prior, and is lower than the national rate,” the DPA writes, citing federal traffic statistics through 2014.
But one challenge to these figures is that marijuana impairment can't be measured via blood tests the same way alcohol impairment can: “it is difficult to establish a relationship between a person's THC [the active psychoactive compound in marijuana] blood or plasma concentration and performance impairing effects,” the National Highway Transit Safety Administration writes.
This is because the active compounds in marijuana are absorbed slowly into the body, and may be detectable in blood samples long after impairment has passed. Post-legalization, if more drivers are testing positive for marijuana that may simply “demonstrate an as-expected increase in marijuana use by adults over 21 years of age in the states that have legalized,” according to the Drug Policy Alliance.
4. Tax revenues have gone up, but make up a small slice of state budgets overall.
By the second year of legalization, marijuana tax revenues exceeded projections in both Colorado and Washington. In the most recent fiscal years, recreational marijuana brought in $129 million in taxes in Colorado and $220 million in Washington.
“These revenues fund school construction, marijuana enforcement and general state needs,” the DPA writes.
Relative to the overall size of the state budgets, these numbers aren't huge — they represent less than 1 percent of total state expenditures in both cases.
The Drug Policy Alliance report doesn't make note of other effects of legalization frequently mentioned by marijuana opponents.
The rate of adult emergency department visits for marijuana use also increased following legalization. This was mostly attributable to more emergency department visits from tourists who had come to the state and had a negative experience with marijuana.