The effect of vertical identification card laws on teenage tobacco and alcohol use
研究垂直身份证法（将21岁以下驾照和身份证改为竖版）对青少年烟草和酒精使用的影响，利用四个全国数据集和精确的法律实施日期，发现该法虽减少零售购买但增加社交获取，总体未降低使用。
We study the impact of vertical identification card laws, which changed the orientation of driver's licenses and state identification cards from horizontal to vertical for those under 21 years, on teenage tobacco and alcohol use. We study this question using four national datasets (pooled national and state Youth Risk Behavior Surveillance System, National Youth Tobacco Survey, Current Population Survey to Tobacco Use Supplements, and Behavioral Risk Factor Surveillance System). We improve previous databases of vertical ID law implementation by using original archival research to identify the exact date of the law change. We estimate models using standard two-way fixed effects and stacked difference-in-differences that avoid bias from dynamic and heterogeneous treatment effects. Using data through 2021, we do not find evidence of reductions in teenage tobacco and alcohol use. While these laws reduce retail-based purchasing, they also increase social sourcing, thus leading to no net impact on use.