Estimation and Inference in Boundary Discontinuity Designs: Distance-Based Methods

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Main Authors: Cattaneo, Matias D., Titiunik, Rocio, Yu, Ruiqi Rae
Format: Preprint
Published: 2025
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author Cattaneo, Matias D.
Titiunik, Rocio
Yu, Ruiqi Rae
author_facet Cattaneo, Matias D.
Titiunik, Rocio
Yu, Ruiqi Rae
contents We study nonparametric distance-based (isotropic) local polynomial methods for estimating the boundary average treatment effect curve, a causal functional that captures treatment effect heterogeneity in boundary discontinuity designs. We establish identification, estimation, and inference results both pointwise and uniformly along the treatment assignment boundary. We show that the geometric regularity of the boundary, a one-dimensional manifold, plays a central role in determining feasible convergence rates and valid inference procedures. Our theoretical contributions are threefold. First, we derive uniform lower and upper bounds on the convergence rate of the misspecification bias of isotropic local polynomial estimators. Second, we obtain uniform distributional approximations that justify boundary-robust inference. Third, we establish minimax lower bounds for a broad class of nonparametric isotropic regression estimators. These results yield practical guidance for empirical implementation, including new bandwidth selection rules that adapt to local irregularities of the treatment-assignment boundary. We illustrate the proposed methods using simulation evidence and an empirical application, and provide companion general-purpose software.
format Preprint
id arxiv_https___arxiv_org_abs_2510_26051
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Estimation and Inference in Boundary Discontinuity Designs: Distance-Based Methods
Cattaneo, Matias D.
Titiunik, Rocio
Yu, Ruiqi Rae
Econometrics
Statistics Theory
Methodology
We study nonparametric distance-based (isotropic) local polynomial methods for estimating the boundary average treatment effect curve, a causal functional that captures treatment effect heterogeneity in boundary discontinuity designs. We establish identification, estimation, and inference results both pointwise and uniformly along the treatment assignment boundary. We show that the geometric regularity of the boundary, a one-dimensional manifold, plays a central role in determining feasible convergence rates and valid inference procedures. Our theoretical contributions are threefold. First, we derive uniform lower and upper bounds on the convergence rate of the misspecification bias of isotropic local polynomial estimators. Second, we obtain uniform distributional approximations that justify boundary-robust inference. Third, we establish minimax lower bounds for a broad class of nonparametric isotropic regression estimators. These results yield practical guidance for empirical implementation, including new bandwidth selection rules that adapt to local irregularities of the treatment-assignment boundary. We illustrate the proposed methods using simulation evidence and an empirical application, and provide companion general-purpose software.
title Estimation and Inference in Boundary Discontinuity Designs: Distance-Based Methods
topic Econometrics
Statistics Theory
Methodology
url https://arxiv.org/abs/2510.26051