Students are considered current marijuana users if they answer “one or more times” to the question, “On how many occasions (if any) have you used marijuana during the last 30 days?” Dropouts and students who were absent on the day of the survey are not included in the results. For detailed analysis of how those omissions may affect results, see Miech, R. A., Johnston, L. D., O’Malley, P. M., Bachman, J. G., Schulenberg, J. E., et al. (2016). Monitoring the Future national survey results on drug use, 1975–2016: Volume I, Secondary school students. Ann Arbor, MI: Institute for Social Research, The University of Michigan. Retrieved from http://www.monitoringthefuture.org/pubs/monographs/mtf-vol1_2016.pdf (Appendix A).
 Johnston, L. D., Miech, R. A., O’Malley, P. M., Bachman, J. G., & Schulenberg, J. E. (2018). Demographic subgroup trends among adolescents in the use of various licit and illicit drugs, 1975–2017 (Monitoring the Future Occasional Paper No. 90). Ann Arbor, MI: Institute for Social Research, The University of Michigan. Retrieved from http://www.monitoringthefuture.org/pubs/occpapers/mtf-occ90.pdf (Tables 13, 14, and 15).
 To derive percentages for each racial/ethnic subgroup, data for the specified year and the previous year have been combined to provide more stable estimates. Estimates for white and black youth exclude Hispanic youth and youth of two or more races. Hispanic youth include persons identifying as Mexican American or Chicano, Cuban American, Puerto Rican, or Other Hispanic or Latino, and no other racial/ethnic group.