It is important to note that, except for coding related to the state of Louisiana, we have not tried to account for cross-state differences in law enforcement or ease of access to alcohol in neighboring states; furthermore, our law coding is based on secondary sources that did not distinguish between furnishing, purchase, possession, and consumption, we do not incorporate the effects of any within-state variation in local drinking ordinances, and (in part because of the uncertainty about state of residence at age 18) we did not distinguish between legal possession of alcohol at ages 18, 19, or 20. Never the less, our ‘reduced form’ analyses do provide an estimate of the average effects of changing MLDA exposures across the United States as they were actually implemented across states and years, and the consistency of our results across age at assessment, survey, gender, ethnicity, family background, and statistical approach provide overall reassurance about the meaningfulness of our findings. Longitudinal data with more exact information about state(s) of residence in late adolescence would control for selective migration, and would allow investigation of
