Why High-Order Polynomials Should Not Be Used in Regression Discontinuity Designs

It is common in regression discontinuity analysis to control for third, fourth, or higher-degree polynomials of the forcing variable. There appears to be a perception that such methods are theoretically justified, even though they can lead to evidently nonsensical results. We argue that controlling...

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Bibliographic Details
Main Authors: Gelman, A. (Author), Imbens, G. (Author)
Format: Article
Language:English
Published: American Statistical Association 2019
Subjects:
Online Access:View Fulltext in Publisher
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001 10.1080-07350015.2017.1366909
008 220511s2019 CNT 000 0 und d
020 |a 07350015 (ISSN) 
245 1 0 |a Why High-Order Polynomials Should Not Be Used in Regression Discontinuity Designs 
260 0 |b American Statistical Association  |c 2019 
856 |z View Fulltext in Publisher  |u https://doi.org/10.1080/07350015.2017.1366909 
520 3 |a It is common in regression discontinuity analysis to control for third, fourth, or higher-degree polynomials of the forcing variable. There appears to be a perception that such methods are theoretically justified, even though they can lead to evidently nonsensical results. We argue that controlling for global high-order polynomials in regression discontinuity analysis is a flawed approach with three major problems: it leads to noisy estimates, sensitivity to the degree of the polynomial, and poor coverage of confidence intervals. We recommend researchers instead use estimators based on local linear or quadratic polynomials or other smooth functions. © 2018, © 2018 American Statistical Association. 
650 0 4 |a Causal identification 
650 0 4 |a Policy analysis 
650 0 4 |a Polynomial regression 
650 0 4 |a Regression discontinuity 
650 0 4 |a Uncertainty 
700 1 |a Gelman, A.  |e author 
700 1 |a Imbens, G.  |e author 
773 |t Journal of Business and Economic Statistics