Tobacco-21 Laws: Impacts on Late Adolescent Smoking

In the past five years, 3 states and over 100 localities have raised their tobacco sales ages to 21. This paper is the first nationally representative analysis to estimate this policy’s effects on late adolescent smoking. Specifically, difference-in-differences analyses use the Behavioral Risk Factor Surveillance System’s Selected Metropolitan/Micropolitan Area Risk Trends (SMART) data to test how age-21 tobacco sales restrictions impact conventional cigarette use among 18 to 20 year olds.

The analytic sample is restricted to metropolitan statistical areas and metropolitan divisions included in every year of the 2011-2015 SMART data. Specifically, these are areas for which the nationally representative BRFSS surveys interviewed at least 500 respondents in each survey-year. As all states adopting age-21 laws implemented their policies in 2016 or later, the analyses presented here are based on policies implemented at the sub-state level. Limiting consideration to 18 to 20 year olds interviewed between 2011 and 2015 yields a sample size of 22,995 respondents, 22,131 of whom responded to the survey’s current smoking questions.

The outcome variable of interest is a binary “current smoker” indicator. For each respondent, the percent of the population covered by an age-21 tobacco sales restriction is calculated for their MMSA-by-state as of their interview date. Difference-in-differences regressions evaluate whether having a higher likelihood of exposure to an age-21 tobacco purchasing restriction yields a differential likelihood of current smoking, controlling for geographic unit and year fixed effects, as well as respondent demographics and an array of other policy variables. This specification passes the requisite parallel trend tests.

Baseline findings indicate that exposure to an age-21 tobacco sales restriction at interview yields a statistically significant 4.8 percentage point drop in one’s likelihood of being a current smoker. Since the vast majority of age-21 laws were implemented in the Northeast and Mid-Atlantic Census Divisions, specification checks restrict the sample to these areas and find a slightly lower but still statistically significant 2.4 percentage point drop in current smoking associated with policy exposure.

Notably, among respondents living in areas with non-zero exposure to tobacco-21 restrictions, the mean likelihood of exposure is only 9.0% in the full sample, as compared to 38.3% in the Northeast and Mid-Atlantic Census Divisions. Thus, for the average respondent who was exposed to these policies, we would expect a 0.4 percentage point drop in smoking relative to unexposed respondents nation-wide (0.048*0.09 = 0.004), versus a 0.9 percentage point drop relative to unexposed respondents in the Northeast and Mid-Atlantic Census Divisions (0.024*0.383 = 0.009).

Falsification tests repeat the main analysis using 23 to 25 year-old respondents, a group not bound by the age-21 restrictions. In this case, age-21 tobacco restrictions yield statistically insignificant effects on current smoking.

Overall, these results indicate that restricting tobacco sales to individuals under age-21 yields a statistically significant reduction in smoking among 18 to 20 year olds, on the order of 0.4 to 0.9 percentage points.