"This paper estimates the impact of fraternity and sorority membership on a wide array of drinking outcomes among respondents to four Harvard College Alcohol Study surveys from 1993-2001. Identification is achieved by including proxies for specific types of unobserved heterogeneity expected to influence the relationship. These include high school and parental drinking behaviors to account for time-invariant omitted factors, and assessed importance of drinking-related activities and reasons for drinking to control for changes in preferences since starting college. Self-selection is quantitatively important. But even controlling for variables plausibly affected by fraternity membership, such as current alcohol use categorization (from abstainer to heavy drinker) and time spent socializing, fraternity membership has a large impact on drinking intensity, frequency and recency, as well as various negative drinking consequences that potentially carry negative externalities"--National Bureau of Economic Research web site.