"Marijuana has been one of the most consistently available drugs and has shown only small variations over the years (see Tables 9-10 through 9-12 and Figure 9-5a). The nine point drop in 12th grade after the pandemic from 79% in 2019 to 70% in 2021 stands out as the largest two-year decrease for this measure over the life of the study. This lower level persisted in 2022. Previous to the pandemic between 80% and 90% of American 12th graders since 1975 reported they could readily obtain marijuana.

"While variability has been small over the course of the survey, perceived availability of marijuana is at or near historic lows in each grade. In 2022 in 8th grade it was 26% (a historic low), in 10th grade it was 49% (the second lowest level recorded by the survey, just above the 2021 low), and in 12th grade it was at 70% (the lowest level ever recorded by the survey). In 10th grade a survey mode effect resulting from the switch to electronic data collection in 2019 indicates estimates based on electronic data collection are seven points lower than those based on paper-and-pencil (see the ‘2019p’ and ‘2019e’ columns in Table 9-11), but even with addition of seven points to the 2021 and 2022 estimates they remain lower than any of the paper-and-pencil estimates since first measured in 1992. These declines in perceived availability are somewhat counter-intuitive and unexpected, given the widespread adoption of medical marijuana laws and recent legalizing of recreational marijuana use for adults in many states. Because most states that have legalized marijuana in some fashion have set a minimum age of 21 for purchase it would apply to the great majority of respondents in grades 8 through 12. Perhaps the emergence of legally sanctioned sale has reduced the size of the market for illicit purchases, resulting in less overall availability to minors."

Source

Miech, R. A., Johnston, L. D., Patrick, M.E., O’Malley, P. M., Bachman, J. G., & Schulenberg, J. E., (2023). Monitoring the Future national survey results on drug use, 1975–2022: Secondary school students. Monitoring the Future Monograph Series. Ann Arbor, MI: Institute for Social Research, University of Michigan.