What happens when employers would like to screen their employees but only observe a subset of output? We specify a model in which heterogeneous employees respond by producing more of the observed output at the expense of the unobserved output. Though this substitution distorts output in the...

What happens when employers would like to screen their employees but only observe a subset of output? We specify a model in which heterogeneous employees respond by producing more of the observed output at the expense of the unobserved output. Though this substitution distorts output in the...

We report the results of a field experiment with bicycle messengers in Switzerland and the United States. Messenger work is individualized enough that firms can choose to condition pay on it, but significant externalities in messenger behavior nonetheless give their on-the-job interactions the...