  This paper reports the results of a series of field experiments designed to
investigate how peer effects operate in a real work setting. Workers were hired
from an online labor market to perform an image-labeling task and, in some
cases, to evaluate the work product of other workers. These evaluations had
financial consequences for both the evaluating worker and the evaluated worker.
The experiments showed that on average, evaluating high-output work raised an
evaluator's subsequent productivity, with larger effects for evaluators that
are themselves highly productive. The content of the subject evaluations
themselves suggest one mechanism for peer effects: workers readily punished
other workers whose work product exhibited low output/effort. However,
non-compliance with employer expectations did not, by itself, trigger
punishment: workers would not punish non-complying workers so long as the
evaluated worker still exhibited high effort. A worker's willingness to punish
was strongly correlated with their own productivity, yet this relationship was
not the result of innate differences---productivity-reducing manipulations also
resulted in reduced punishment. Peer effects proved hard to stamp out: although
most workers complied with clearly communicated maximum expectations for
output, some workers still raised their production beyond the output ceiling
after evaluating highly productive yet non-complying work products.
