Research

Dr Eyo Herstad, Erasmus Rotterdam

"Identification of Heterogeneous Peer Effects"
Friday, 30 October 2026. 15:00
Room G56 Sem 1, Kelvin Hall building

Abstract

We develop a model of peer effects where each peer has a separate effect depending on their rank in the distribution of peers' outcomes. Our model admits a unique equilibrium, and model parameters can be identified using peers' exogenous characteristics. To obtain a more parsimonious model of peer effects, we introduce a tractable specification based on quantile-dependent peer effect coefficients, and develop a specification test. Applying the model to several student outcomes in the Add Health data, we uncover heterogeneous and often non-monotonic spillovers that cannot be captured by existing models. Our results have direct implications for counterfactual analysis, suggesting that a student's influence in a network depends not only on network structure, but also on that student's position in the outcome distribution of their peers. We also provide an R package, QuantilePeer, that implements our methods.

Bio

Eyo Herstad is an assistant professor at the Econometrics Institute of Erasmus School of Economics and a candidate fellow at the Tinbergen Institute. He earned his master’s degree in economics from the University of Oslo and completed his Ph.D. in Economics at the University of Chicago. Prior to his current role, Herstad was a postdoctoral researcher at The Ohio State University.

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First published: 15 September 2026