Students were considered daily cigarette smokers if they indicated that they smoked one or more cigarettes per day in the last 30 days.
Students were considered e-cigarette smokers if they indicated they used any e-cigarettes in the past 30 days. The question referred to “electronic cigarettes or e-cigarettes.”
 Johnston, L. D., O’Malley, P. M., Bachman, J. G., & Schulenberg, J. E. (2011). Monitoring the future: National results on adolescent drug use, Overview of key findings. Ann Arbor, MI: Institute for Social Research. Retrieved from http://www.monitoringthefuture.org/pubs/monographs/mtf-overview2010.pdf.
 Wang, T. W., Gentzke, A., Sharapova, S., Cullen, K. A., Ambrose, B. K., et al. (2018). Tobacco product use among middle and high school Students — United States, 2011–2017. Morbidity and Mortality Weekly Report, 67(22), 629–633. Retrieved from https://www.cdc.gov/mmwr/volumes/67/wr/mm6722a3.htm.
 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.
Child Trends Databank. (2018). Daily cigarette use. Retrieved from: https://www.childtrends.org/?indicators=daily-cigarette-use