Legalizing recreational marijuana has had minimal effect on crime rates in Colorado and Washington, according to a study funded by the U.S. federal government.

The Department of Justice commissioned researchers from Washington State University, the University of Utah and Stockton University to conduct the study, which was published today. Colorado and Washington were the first two states to permit adult-use cannabis, so they became the focus of the research.

The team analyzed monthly crime rates as compiled in the FBI’s Uniform Crime Reports from 1999 to 2016. It compared this data with monthly crime rates to those in 21 states where recreational and medicinal marijuana use remains illegal to draw conclusions on its impact upon violent and property crime.

The study found no statistically significant long-term effects of legal recreational cannabis sales crime rates in either state. Washington actually saw a decline in burglary rates, so potential burglars may have decided against robbing houses after getting stoned.

The findings suggest legalization and sales of marijuana have had minimal effect on major crimes in both states.

“This is but one study and legalization of marijuana is still relatively new, but by replicating our findings, policymakers can answer the question of how legalization affects crime,” said one of the authors, Dale W. Willits, an assistant professor of criminal justice and criminology at WSU.

Lead author Ruibin Lu, an assistant professor of criminal justice at Stockton University, said the team felt it was important to apply “robust empirical methods” to parse out the effects of this action on crime in the first years after legalization.

The researchers said they feel their research is robust, and that the legalization of marijuana has not resulted in a significant upward trend in crime rates, contrasting previous studies on the same topic.

Oregon, Alaska, California, Maine, Massachusetts, Nevada, Michigan, Vermont, and Illinois have joined Colorado and Washington in legalizing recreational cannabis use, and campaigns are afoot to see it permitted elsewhere in the U.S.