MINNEAPOLIS (WCCO) — Since 2012, eight states and the District of Columbia have made recreational marijuana legal.

On Thursday morning, Minnesota legislators introduced two bills that would seek to change the law in Minnesota. What has the impact of legalizing recreational marijuana been in states that have tried it? Good Question.

“For the most part, we don’t have enough data to have a complete picture,” says Mark Bolton, who heads the marijuana legalization office for Colorado Governor John Hickenlooper. He says the state started collecting data in 2012 once the law passed, but much of that data is considered baseline.

Several studies have been done showing different results regarding marijuana usage and traffic safety.

Study: Legalization of Marijuana in Colorado

Dose of Reality: The Effect of State Marijuana Legalizations

What We Know About Marijuana Legalization

“It’s not possible to know the effects of legalization because there are a broad range of policies,” says Mark A.R. Kleiman, a professor at NYU who has studied the effect of marijuana policy.  He points out researchers must look at the different types of stores, training of clerks, prices and marketing in the various commercial systems.

According to the Tax Foundation, Colorado brought in $171 million in tax revenue last year and Washington State was expected to bring in $270 million.  That’s still a small portion of each state’s $40 billion budgets.

“The question becomes how is each state taxing it?” says Ryan Steel, a marijuana policy researcher at the University of Minnesota. “That becomes where do we find the right taxation rate.”

A study by the Drug Policy Alliance found arrests for marijuana offenses are down, but the racial disparities among the remaining arrests still exist.

There are also several ways to look at impaired driving – whether through arrests or fatal accidents. The difficulty with those statistics is that there isn’t yet a good way to measure marijuana in a person’s system.

Statistics on teen usage have also varied. According to a study in JAMA, teen usage in Colorado declined after legalization and increased in Washington.  Nationally, teen usage of marijuana has remained flat or falling.

Heather Brown