Peer Effects and Alcohol Use among College Students

This paper examines the extent to which college students who drink alcohol influence their peers. We exploit a natural experiment in which students at a large state university were randomly assigned roommates through a lottery system. We find that on average, males assigned to roommates who reported drinking in the year prior to entering college had a Grade Point Average (GPA) one quarter-point lower than those assigned to nondrinking roommates. The effect of initial assignment to a drinking roommate persists into the second year of college and possibly grows. The effect is especially large for students who drank alcohol themselves in the year prior to college. In contrast to the males, females' GPAs do not appear affected by roommates' drinking prior to college. Furthermore, students' college GPA is not significantly affected by roommates' high school grades, admission test scores, or family background. These findings are more consistent with models in which peers change people's preferences than with models in which peers change people's choice sets. Surprisingly, the policy of segregating drinkers by having substance-free housing could potentially lower average GPA in the university.