The effect of alcohol availability on marijuana use: evidence from the minimum legal drinking age.

This paper exploits the discontinuity created by the minimum legal drinking age of 21 years to estimate the causal effect of increased alcohol availability on marijuana use. We find that consumption of marijuana decreases sharply at age 21, while consumption of alcohol increases, suggesting that marijuana and alcohol are substitutes. We further find that the substitution effect between alcohol and marijuana is stronger for women than for men. Our results suggest that policies designed to limit alcohol use have the unintended consequence of increasing marijuana use.