Optimal and Structure-Adaptive CATE Estimation with Kernel Ridge Regression

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1. Verfasser: Kim, Seok-Jin
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Veröffentlicht: 2026
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author Kim, Seok-Jin
author_facet Kim, Seok-Jin
contents We propose an optimal algorithm for estimating conditional average treatment effects (CATEs) when response functions lie in a reproducing kernel Hilbert space (RKHS). We study settings in which the contrast function is structurally simpler than the nuisance functions: (i) it lies in a lower-complexity RKHS with faster eigenvalue decay, (ii) it satisfies a source condition relative to the nuisance kernel, or (iii) it depends on a known low-dimensional covariate representation. We develop a unified two-stage kernel ridge regression (KRR) method that attains minimax rates governed by the complexity of the contrast function rather than the nuisance class, in terms of both sample size and overlap. We also show that a simple model-selection step over candidate contrast spaces and regularization levels yields an oracle inequality, enabling adaptation to unknown CATE regularity.
format Preprint
id arxiv_https___arxiv_org_abs_2602_18958
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Optimal and Structure-Adaptive CATE Estimation with Kernel Ridge Regression
Kim, Seok-Jin
Methodology
Statistics Theory
Machine Learning
We propose an optimal algorithm for estimating conditional average treatment effects (CATEs) when response functions lie in a reproducing kernel Hilbert space (RKHS). We study settings in which the contrast function is structurally simpler than the nuisance functions: (i) it lies in a lower-complexity RKHS with faster eigenvalue decay, (ii) it satisfies a source condition relative to the nuisance kernel, or (iii) it depends on a known low-dimensional covariate representation. We develop a unified two-stage kernel ridge regression (KRR) method that attains minimax rates governed by the complexity of the contrast function rather than the nuisance class, in terms of both sample size and overlap. We also show that a simple model-selection step over candidate contrast spaces and regularization levels yields an oracle inequality, enabling adaptation to unknown CATE regularity.
title Optimal and Structure-Adaptive CATE Estimation with Kernel Ridge Regression
topic Methodology
Statistics Theory
Machine Learning
url https://arxiv.org/abs/2602.18958