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.

烟草 21 (T-21) 法律将所有烟草产品的最低合法购买年龄提高至 21 岁。这项研究首次探讨了全州范围内的 T21 法律对青少年和年轻人卷烟和电子烟 (e-香烟) 使用的影响。使用行为风险因素监测系统 (BRFSS) 的调查数据和双重差分法，我们发现全州范围内采用 T-21 法律与吸烟参与率下降 2 至 4 个百分点相关。 18至20岁的年轻人。使用州青少年风险行为调查 (YRBS) 进行的补充分析表明，随着 T21 法律的通过，18 岁青少年电子烟的使用频率也有所下降，尽管这种影响部分是因为青少年转向非正式的社会来源来获取电子烟。香烟（即借用或吸烟）。最后，我们发现 T-21 法律产生了溢出效应，包括 (2) 减少 16 至 17 岁青少年（该群体在高中严重依赖非正式社会市场）的吸烟量，以及 (2) 减少一些青少年吸食大麻和酗酒的情况。