Estimating the effects of tobacco-21 on youth tobacco use and sales.

We examine the effect of raising the minimum legal sale age of tobacco to 21 (i.e., "T21"). We estimate difference-in-differences models using the Monitoring the Future (MTF) survey data and Nielsen Retail Scanner data from 2012 to 2019. Outcomes include cigarette and e-cigarette use and sales. We find sizable reductions in e-cigarette and cigarette use for 12th graders. T21 also reduced cigarette sales by 12.4 % and e-cigarette sales by 69.3 % in counties with the highest percent quartile of individuals under 21 years of age. In terms of mechanisms, we find that T21 increases ID checking and perceived risks of using both products.