The Washington State Institute for Public Policy is directed to conduct a benefit-cost analysis of the implementation of I-502, which legalizes recreational cannabis use for adults within the state. As a preliminary step, we analyzed population-level data to begin monitoring four key indicators of cannabis use prior to implementation.
We used data from the 2002 to 2011 administrations of the National Survey on Drug Use and Health to examine trends in the prevalence of current cannabis use, lifetime cannabis use, age of initiation, and cannabis abuse or dependency. We examined these trends separately for youth and adults in Washington, and also provide estimates for Colorado (the other state that has legalized recreational cannabis use) and the rest of the United States (US).
Examining trends in this manner will allow us to monitor whether the implementation of I-502 appears to affect these key indicators of marijuana use over time. Although more sophisticated analyses will be required for us to evaluate the policy, these initial trends provide a baseline to compare future data against.
The prevalence of cannabis use in the past 30 days—a key indicator of the proportion of people who are current cannabis users—appears to be on the rise in recent years among both youth and adults in Washington, Colorado, and the US. The other indicators of use appear to be relatively stable or increasing slightly over time. In general, the estimates from Washington are slightly higher than the US and slightly lower than Colorado.
We will continue to monitor these trends over time within the context of our larger benefit-cost analysis to examine whether the new policy appears to affect marijuana use rates within the state.