Do tobacco 21 laws work?

Tobacco 21 (T-21) laws raise the minimum legal purchasing age for all tobacco products to 21. This study is the first to examine the impact of statewide T21 laws on teenage and young adult cigarette and electronic cigarette (e-cigarette) use. Using survey data from the Behavioral Risk Factor Surveillance System (BRFSS) and a difference-in-differences approach, we find that statewide adoption of a T-21 law is associated with a 2-to-4 percentage-point decline in smoking participation among 18-to-20-year-olds. Supplemental analyses using the State Youth Risk Behavior Surveys (YRBS) show that frequent e-cigarette use among 18-year-olds also fell following the adoption of T21 laws, though this effect was partially because teens turned to informal social sources to obtain e-cigarettes (i.e., borrowing or bumming). Finally, we find that T-21 laws generate spillover effects, including (2) reductions in cigarette use among 16-to-17-year-olds, a group that relies heavily on informal social markets in high school, and (2) reductions in marijuana use and days of alcohol use among some teens.