Monday, September 21, 2015

Kremer and Levy (2008) on Peer Effects and Alcohol

Michael Kremer and Dan Levy, “Peer Effects and Alcohol Use Among College Students.” Journal of Economics Perspectives 22(3): 189-206, Summer, 2008.

• The data come from a large state university that randomly assigns some roommates. The finding: males assigned roommates who drank in high school had a lower GPA. 

• By using high school characteristics, we can rule out that the GPA connection stems from common shocks to the roommates. 

• For the most part, studies don’t find much support for the idea that academic characteristics affect the academic performance of roommates. Kremer and Levy likewise find no effect of academic background or social background on roommate academic achievement. 

• The GPA decline for males is about .27 if the roommate drank in high school. The drop is especially bad for weak students, and for those who themselves drank in high school, and it’s much greater in the second year (though you are no longer roommates). 

• Roommates who are not randomly assigned, but who choose each other, do not see falls in GPA from roommate drinking history. 

• Reducing the drinking of one student can reduce the drinking of others. But collecting non-drinkers in substance-free housing will concentrate the drinking students, with a negative effect on overall GPAs.

Falk and Ichino (2006), “Clean Evidence on Peer Effects”

Armin Falk and Andrea Ichino, “Clean Evidence on Peer Effects [pdf].” Journal of Labor Economics 24(1): 39-57, 2006.

• Observational methods make it hard to separate out peer effects from birds of a feather flocking together, or from a shared environment. 

• Here, the authors use random assignment to either a peer setting or to a solo task; the task is envelope stuffing. The existence of peer effects would lead to stronger correlation between peers than between unmatched others. 

• The authors find the requisite correlation, as well as evidence that the peer effects raise average productivity (mainly by raising the output of the less productive person). 

• The workers were Swiss high school students, given the envelope-stuffing job that paid more than $60 for a four-hour session. Peers worked separately but near each other. The total number of participants was but 24, eight of whom were in the solo condition. 

• They find that if one peer raises output by one unit, the other person raises output by .14 unit. 

• Would a non-working peer also tend to increase the output of a worker, by providing a sort of supervision?