This paper is a practical guide for researchers and practitioners who want to understand spillover effects in program evaluation. The paper defines spillover effects and discusses why it is important to measure them. It explains how to design a field experiment to measure the average effects of...

How do peers influence the impact of incentives? Despite much work on incentives, little is known about the spillover effects of incentives. We investigate two mechanisms by which these effects can occur: through peers' actions and peers' incentives. In a field experiment on snack choice (grapes...