The effects of tobacco 21 laws on smoking and vaping: Evidence from panel data and biomarkers.

We use data from the Population Assessment of Tobacco Use and Health (PATH), a longitudinal data set including self-reported and biomarker measures of tobacco use, to examine the effects of state-level tobacco 21 (T21) laws on smoking and vaping. T21 laws reduce self-reported cigarette smoking among 18-to-20 year olds, concentrated in males. Initial non-users who "age-out" of treatment are less likely to subsequently initiate self-reported smoking or vaping. Treated smokers are less likely to buy their own cigarettes and more likely to buy cigarettes in a different state. Biomarker results are mixed, and we find some evidence of a reduction in nicotine exposure but less evidence for a reduction in exposure to tobacco. Finally, we test for non-classical measurement error. T21 laws reduce the probability that clinically identified likely cigarette smokers self-report as smokers, which may increase the apparent effect of T21 laws on cigarette smoking as measured by self-reports.