Am I My Brother's Barkeeper? Sibling Spillovers in Alcohol Consumption at the Minimum Legal Drinking Age

We use data on sibling pairs near the minimum legal drinking age to provide causal estimates of peer effects in alcohol consumption. Following prior work on other outcomes, we exploit the discontinuous increase in alcohol consumption of the older sibling at the legal drinking age in a regression discontinuity design. Our preferred point estimates imply that the number of binge drinking days reported by the younger sibling decreases by 27% of the mean at the cutoff. While our estimates are somewhat imprecise, we are consistently able to rule out positive estimates from the existing literature. Our research design provides estimates which are interpretable as the causal effect of the peer's alcohol consumption. This is in contrast to most prior work which instead identifies the causal effect of exposure to the peer. We explain how this distinction matters for policy.