Subgroups Matter for Robust Bias Mitigation

Fuente: arXiv
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Main Authors: Alloula, Anissa, Jones, Charles, Glocker, Ben, Papież, Bartłomiej W.
Format: Preprint
Published: 2025
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author Alloula, Anissa
Jones, Charles
Glocker, Ben
Papież, Bartłomiej W.
author_facet Alloula, Anissa
Jones, Charles
Glocker, Ben
Papież, Bartłomiej W.
contents Despite the constant development of new bias mitigation methods for machine learning, no method consistently succeeds, and a fundamental question remains unanswered: when and why do bias mitigation techniques fail? In this paper, we hypothesise that a key factor may be the often-overlooked but crucial step shared by many bias mitigation methods: the definition of subgroups. To investigate this, we conduct a comprehensive evaluation of state-of-the-art bias mitigation methods across multiple vision and language classification tasks, systematically varying subgroup definitions, including coarse, fine-grained, intersectional, and noisy subgroups. Our results reveal that subgroup choice significantly impacts performance, with certain groupings paradoxically leading to worse outcomes than no mitigation at all. Our findings suggest that observing a disparity between a set of subgroups is not a sufficient reason to use those subgroups for mitigation. Through theoretical analysis, we explain these phenomena and uncover a counter-intuitive insight that, in some cases, improving fairness with respect to a particular set of subgroups is best achieved by using a different set of subgroups for mitigation. Our work highlights the importance of careful subgroup definition in bias mitigation and presents it as an alternative lever for improving the robustness and fairness of machine learning models.
format Preprint
id arxiv_https___arxiv_org_abs_2505_21363
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Subgroups Matter for Robust Bias Mitigation
Alloula, Anissa
Jones, Charles
Glocker, Ben
Papież, Bartłomiej W.
Machine Learning
Artificial Intelligence
Despite the constant development of new bias mitigation methods for machine learning, no method consistently succeeds, and a fundamental question remains unanswered: when and why do bias mitigation techniques fail? In this paper, we hypothesise that a key factor may be the often-overlooked but crucial step shared by many bias mitigation methods: the definition of subgroups. To investigate this, we conduct a comprehensive evaluation of state-of-the-art bias mitigation methods across multiple vision and language classification tasks, systematically varying subgroup definitions, including coarse, fine-grained, intersectional, and noisy subgroups. Our results reveal that subgroup choice significantly impacts performance, with certain groupings paradoxically leading to worse outcomes than no mitigation at all. Our findings suggest that observing a disparity between a set of subgroups is not a sufficient reason to use those subgroups for mitigation. Through theoretical analysis, we explain these phenomena and uncover a counter-intuitive insight that, in some cases, improving fairness with respect to a particular set of subgroups is best achieved by using a different set of subgroups for mitigation. Our work highlights the importance of careful subgroup definition in bias mitigation and presents it as an alternative lever for improving the robustness and fairness of machine learning models.
title Subgroups Matter for Robust Bias Mitigation
topic Machine Learning
Artificial Intelligence
url https://arxiv.org/abs/2505.21363