Finally, we tested whether cross-state migration could be a confounder of the apparent MLDA effect, using information about state of birth and state of residence in the NLAES and in the US Census. Supplementary figure 2 compares the proportion of respondents in the target cohort who were no longer living in their birth state in the 1991–92 NLAES sample and in the 1970 through 2000 US Census. We found that 63.1% of NLAES respondents were still living in their state of birth; 22.4 % were no longer living in their state of birth, but would have had no change in their MLDA status, and 14.5 % would have changed their MLDA exposure status in moving from birth state to present state. The trends were similar in the US Census, which shows two peaks in cross-state migration, the first between birth and age five, and the second between 18 and 21. Even in the large Census sample, respondents who would have been exposed to an earlier legal drinking age in their birth states were no more or less likely to migrate
