Legalizing marijuana has the potential to reduce crime by shifting the production, sale, and consumption of marijuana from the illegal market to a regulated system. In recent years, several studies have demonstrated the strong association between the passage of marijuana laws and reductions in crime. In 2017, researchers from the Federal Reserve Bank of Philadelphia analyzed the impact of marijuana dispensary openings on neighborhood crime rates in Denver, CO. Ultimately, the researchers found that crime rates declined 19% in neighborhoods after a marijuana dispensary opened.
Source: Brinkman, Jeffrey, and David Mok-Lamme. Not in My Backyard? Not So Fast. The Effect of Marijuana Legalization on Neighborhood Crime. Working paper. Philadelphia: Research Department, Federal Reserve Bank of Philadelphia, 2017. Federal Reserve Bank of Philadelphia, Philadelphia. 12 Feb. 2019 https://www.philadelphiafed.org/-/media/research-and-data/publications/working-papers/2017/wp17-19.pdf