The Freakonomics of Pot and DUIs

States that have legalized medical cannabis have fewer traffic deaths than those that haven't. Plus, The Discovery Channel has a hit with "Weed Wars."

A controversial new study by two economists indicates that medical marijuana legalization laws have resulted in a 9 percent drop in traffic deaths — and a 5 percent reduction in beer sales. The study reveals that driving in states that have legalized medical cannabis is safer than in those where medical pot remains unlawful.

It’s a contrarian case of Freakonomics that’s sure to invite scrutiny. Co-author Daniel Rees, an economics professor at the University of Colorado, Denver, is the first to admit he didn’t expect the results, but he also stands by them. “If critics want to collect the data themselves, boy, the results will jump out at them the way they jumped out at us,” he said. “Our results are pretty robust. We’re pretty confident they’re going to hold up.”

Rees, along with D. Mark Anderson, an assistant professor of economics at Montana State University, used government statistics on road fatalities and drug behavior to look at what happened between 1990 and 2009 in thirteen states that have legalized medical marijuana compared to those that haven’t. They found that the safety effect of legalization is comparable to gains from increasing the legal drinking age to 21, or mandating seat belts for those ages 14 to 18. The safety effect is even greater in the groups most at risk for road fatalities: young, male, intoxicated, weekend night drivers. “Legalization is associated with a 19 percent decrease in the fatality rate of 20-29 year-olds,” the study stated.

That was not Rees’ hypothesis. “Include us in that group who thought, ‘This is going to be crash central,'” he said of states that had legalized medical weed. “We were totally surprised when the results came out so strong in the other direction.”

Both Rees and Anderson have experience studying risk behavior among youth: Anderson worked on explaining methamphetamine’s decline in other states and Rees has worked on papers about marijuana and alcohol use.

Using data from the Behavioral Risk Factor Surveillance System from the Centers for Disease Control and Prevention, the researchers also found that medical marijuana laws “are associated with decreases in the number of drinks consumed, especially among 20- through 29-year-olds. … Using data from the Beer Institute, we find beer sales fell after [legalization] comes into effect, suggesting marijuana substitutes for beer, the most popular alcoholic beverage among adults.”

The drop in drinking and the safety effect in the groups most associated with alcohol-involved road fatalities were so large “that a light bulb went off: ‘Oh, what’s going on? People are switching from alcohol to marijuana,'” Rees said.

Rees speculates that young males are the early adopters when medical marijuana laws change. As the overall climate of prohibition cools in a state, young men, the most likely to end up in fatal traffic accidents, are switching from booze to weed. “My suspicion is as soon as you open the door to individuals growing [medical] marijuana, you’ve opened the door to diversion to the recreational markets.” The paper asserts, and studies show, that driving while stoned is safer than driving drunk.

Obviously, the study’s results are not going to play well with the federal prosecutors and law enforcement lobbyists. The oldest and most frequent rebuttal to legalization is that it will lead to “road carnage,” and critics are sure to try to find flaws with the new study.

For example, the study, which was funded by the Institute for the Study of Labor in Bonn, Germany, a research center focused on labor economics and policy, was not peer reviewed, Rees said. He and Anderson published it as a working paper for a number of reasons, including getting it out first (he said a number of researchers are working on the topic). “If our critics wanted to call it a work in progress our answer would be, ‘Yes.'” he said.

Another potential flaw with the study is the sheer number of different flavors of legalization there are in America. Vermont’s program, for example, is very different from California’s.

Rees says they weighted states by population and results are overall averages. Critics, however, may also question if there are enough pot users to account for the drop in deaths, Rees said. There are, he says.

Lastly, correlation does not equal causation, of course, so the team used a difference-in-difference analysis to account for broader national and state trends — like the recent reduction in road fatalities nationwide — Rees said. But even so, “traffic fatalities fall by nearly 9 percent after the legalization of medical marijuana,” the study stated.

“Clearly policy makers, the public, concerned mothers, we all want roads to be safer,” Rees said. “I do think there’s a certain irony if it turns out that, indeed, medical marijuana is driving a reduction in traffic fatalities. Often policy is not driven by data or logic. It this study can inform policy in a positive way I’d be happy.”

A PDF of the study from the Institute for the Study of Labor is available on the Express‘ website. We’ll follow up when it and others like it get published.

Seeds and Stems

Chalk it up to the slow news season, plus a juicy federal crackdown, but The Discovery Channel’s Weed Wars has popped off on cable TV. The reality series, filmed at Oakland’s Harborside Health Center, debuted to a ton of mostly positive press on December 1, and the second of four episodes runs on Thursday, December 8. The first episode introduced owner Stephen DeAngelo and staff. This week, DeAngelo confronts a $2.5 million IRS tax bill for “drug trafficking.” Check your local listings.


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