Abstract Christian Saenz is currently a PhD student in Economics at Georgia State University and will have a major role in this administrative supplement. Christian aspires to become an independent health economist and addiction researcher. Saenz will receive detailed training in career development and in conducting tobacco policy and addiction research as part of this supplement. The parent grant’s aims are as follows: (1) estimate the effect of flavor bans with varying levels of strength on youth e-cigarette use, combustible tobacco product use, and substitution towards the remaining legally available flavored tobacco products; (2) estimate the effect of Tobacco-21 laws on youth e-cigarette use, combustible tobacco product use, and source of e-cigarettes; and (3) estimate the effect of e-cigarette taxes, including new e-cigarette tax schema of sales taxes and two-tier taxes, on youth e-cigarette use and CTP use. This proposed administrative supplement will complement the parent grant’s aims by exploring how e-cigarette tax responsiveness is impacted by out-of-state and Indian reservation purchasing, by identifying specific components of Tobacco-21 laws that make them more effective, and by identifying the effect of e-cigarette introduction in 2006 on short- and medium-term smoking-attributable mortality. The research proposal will leverage high quality survey data, restricted-use mortality data, and proprietary Nielsen Homescan and Retail Scanner panel data, to study these questions. This research is significant because it will provide insight into the economic substitution or complement relationship between e-cigarettes and relatively more dangerous combustible tobacco; estimate heterogeneity in effectiveness of state T21 legislation based on the strength or ‘bite’ of three specific components of the bundled legislation, identify the elements of optimal T21 regulation; determine how tax avoidance behaviors affect e-cigarette tax responsiveness; and estimate short- and medium-term smoking-attributable mortality effects of the e-cigarette entry in the U.S. market in 2006. This research, if funded, would be innovative by using recent innovations on the differences-in-differences model designed to mitigate bias from heterogeneous treatment effects and endogeneity bias such as Callaway and Sant’Anna estimators and event study designs; by answering novel research questions using proprietary data, and estimating state policy heterogeneity in order to inform future legislative efforts.