Why High-order Polynomials Should not be Used in Regression Discontinuity Designs

NBER Working Paper No. 20405

Issued in August 2014

NBER Program(s):Labor Studies



It is common in regression discontinuity analysis to control for high order (third, fourth, or higher) polynomials of the forcing variable. We argue that estimators for causal effects based on such methods can be misleading, and we recommend researchers do not use them, and instead use estimators based on local linear or quadratic polynomials or other smooth functions.

Acknowledgments and Disclosures

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Document Object Identifier (DOI): 10.3386/w20405

Published: Andrew Gelman & Guido Imbens (2017) Why high-order polynomials should not be used in regression discontinuity designs, Journal of Business & Economic Statistics, DOI: 10.1080/07350015.2017.1366909 citation courtesy of

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