Peers Matter

Peer effects are a hot research topic.

According to a new working paper by Alexandre Mas and Enrico Moretti, a person works harder when he has hard-working peers:

Using scanner level data, we measure high frequency, worker-level productivity of checkers for a large grocery chain. Because of the firm's scheduling policy, the timing of within-day changes in personnel is unsystematic, a feature for which we find consistent support in the data. We find strong evidence of positive productivity spillovers from the introduction of highly productive personnel into a shift. A 10% increase in average co-worker permanent productivity is associated with 1.7% increase in a worker's effort.

According to a new working paper by Philip J. Cook, Robert MacCoun, Clara Muschkin, and Jacob Vigdor, whether sixth graders are grouped with younger kids in elementary school or older kids in middle school affects their behavior:

sixth grade students attending middle schools are much more likely to be cited for discipline problems than those attending elementary school....Furthermore, the higher infraction rates recorded by sixth graders who are placed in middle school persist at least through ninth grade. A plausible explanation is that sixth graders are at an especially impressionable age; in middle school, the exposure to older peers and the relative freedom from supervision have deleterious consequences.

To read about earlier work on peer effects, click here and here.

These results would not surprise Judith Rich Harris.