Cited by 193Ethics and Social Impacts of AIExplainable Artificial Intelligence (XAI)Privacy-Preserving Technologies in Data

The DOI matches its Crossref record; 33 of the 37 references it cites were found in a registry or an index; none of the 16 sources its claims cite is checked for support yet.

Multiaccuracy: Black-Box Post-Processing for Fairness in Classification

Open access
Kim, Michael P., Ghorbani, Amirata, Zou, James·2019·Proceedings of the 2019 AAAI/ACM Conference on AI, Ethics, and Society

Abstract

Prediction systems are successfully deployed in applications ranging from disease diagnosis, to predicting credit worthiness, to image recognition. Even when the overall accuracy is high, these systems may exhibit systematic biases that harm specific subpopulations; such biases may arise inadvertently due to underrepresentation in the data used to train a machine-learning model, or as the result of intentional malicious discrimination. We develop a rigorous framework of *multiaccuracy* auditing and post-processing to ensure accurate predictions across *identifiable subgroups*. Our algorithm, MULTIACCURACY-BOOST, works in any setting where we have black-box access to a predictor and a relatively small set of labeled data for auditing; importantly, this black-box framework allows for improved fairness and accountability of predictions, even when the predictor is minimally transparent. We prove that MULTIACCURACY-BOOST converges efficiently and show that if the initial model is accurate on an identifiable subgroup, then the post-processed model will be also. We experimentally demonstrate the effectiveness of the approach to improve the accuracy among minority subgroups in diverse applications (image classification, finance, population health). Interestingly, MULTIACCURACY-BOOST can improve subpopulation accuracy (e.g. for "black women") even when the sensitive features (e.g. "race", "gender") are not given to the algorithm explicitly.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

The paper introduces multiaccuracy, a black-box post-processing framework that audits a classifier for systematic bias across identifiable subpopulations and iteratively updates it with Multiaccuracy Boost. It proves convergence and do-no-harm guarantees and shows improved subgroup accuracy in gender detection, adult income, and semi-synthetic disease prediction without requiring sensitive features.

Key findings

  • On PPB gender detection, the initial model had 9.9% overall error but 39.8% error on dark-skinned females and 0.0% on light-skinned males; Multiaccuracy Boost reduced overall error to 3.9% and dark-skinned female error to 12.5%, while light-skinned male error changed from 0.0% to 0.8%.
  • On Adult Income, Multiaccuracy Boost improved overall error from 19.3% to 14.7% and improved each subgroup, outperforming subgroup-specific models (SS overall 19.7%); for example, Black female error went from 4.8% to 4.5% (SS 5.5%).
  • On semi-synthetic UK Biobank disease prediction, Multiaccuracy Boost lowered overall error from 18.9% to 16.0% and old female error from 36.8% to 26.5%, better than subgroup-specific models (SS old female 37.6%).
  • Theoretically, the do-no-harm guarantee bounds post-processed error on an audited subpopulation as er_S(f;y) ≤ 3·er_S(f0;y) + 4β, and Algorithm 1 converges to a (C, α)-multiaccurate hypothesis in T = O(ℓ_D(f0;y)/α²) iterations from m = Õ(T·d(C)+log(1/δ)/α²) samples.

Methods

  • Setting: black-box access to f0 and a small labeled validation sample from D; an auditor A learns a class C to find functions h correlating with the residual f−y; Multiaccuracy Boost partitions X by f0 into X0 and X1, audits X, X0, and X1, selects the largest residual, and applies multiplicative weights updates until (C, α)-multiaccuracy is reached.
  • Experiments: Gender detection used an inception-resnet-v1 trained on CelebA (>200,000 images; 98.4% test accuracy), audited on PPB (415 test, 855 audit) with ridge regression on a VAE/Facenet representation, compared to white-box retraining of the last two layers. Adult Income used 45,222 samples and 14 attributes, with 27,145 training, 15,060 test, and 3,017 audit samples, decision tree regression (max depth 5), and sensitive features removed. Semi-synthetic disease prediction used 40,000 UK Biobank individuals with 60 phenotype features, four gender-age groups with polynomial label functions of orders 1, 4, 2, and 6, 32,000 training and 4,000 audit samples, and decision tree regression.
  • Analysis: theoretical proofs of Proposition 1, Theorem 2, and Theorem 3 are given in the appendix; empirical evaluation reports classification error on overall and subgroup populations in Tables 1–3.

Limitations

  • Stated: Multiaccuracy works only to the extent that the auditor can identify subgroups where f0 tends to make mistakes; if the mistakes appear overly complicated to the bounded auditor, the auditor will not identify them. The paper also notes that one must balance the choice of C and the number of iterations to avoid overfitting, and that if the auditor learns an expressive enough class, the algorithm will start to overfit at some point.
  • Stated: The theory assumes fresh samples per iteration, and in practice with few samples one may need noise-addition techniques to reduce overfitting. The data distribution D should reflect the true population or be aspirational, and important subpopulations must be sufficiently represented; the classification error guarantee improves as γ, the density of the protected subpopulation, grows. In the gender detection case study, CelebA lacks race labels, so subpopulation accuracy could not be evaluated on that set, and PPB is described as very small and a stress test.
  • Evident: Empirical validation is limited to binary classification tasks and specific datasets; effectiveness depends on audit features being correlated with unobserved sensitive categories, as the paper states. Formal guarantees also depend on A agnostically learning the class C.

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Integrity signals

Registry

Crossref · 10.1145/3306618.3314287

Cites

33 of 33 references verified0 citation errors · 0 not checkable

Statistics

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Claims the paper makes

40 Own interpretation · 19 Own result · 16 No basis given · 14 Not checked yet

Verify all 16 references — free account

Show all 61 claims

  • It may state two separate claims as one. 19
  • Probably not a substantial claim. 12
28 of 28
  • The authors state this as an assumption.

    The important subpopulations are sufficiently represented in the validation data distribution D.

    “we assume that the important subpopulations are sufficiently represented on D”
  • The authors state this as an assumption.

    The auditing algorithm A uses a fresh sample D_t ∼ D^m per iteration.

    “we assume that A uses a fresh sample D t ∼ D m per iteration.”
  • The authors state this as an assumption.

    The auditing algorithm A can identify a very rich class of overlapping sets.

    “As we assume A can identify a very rich class of overlapping sets”
  • The paper relies on this without support.

    Data from certain minority populations is less available than from the majority population.

    “often for historical and social reasons, data from certain minority populations is less available than from the majority population.”
  • The paper relies on this without support.

    In the common setting where the learned model is provided as a service, there may not be sufficient incentive for the service provider to retrain the model.

    “there may not be sufficient incentive (financial, social, etc.) for the service provider to retrain the model.”
  • The paper relies on this without support.

    In many applications, race or more granular categories are not given.

    “This is not feasible in the many applications where, say, race or more granular categories are not given.”
  • The paper relies on this without support.

    Even when subgroups are identified, there are often not enough samples to train accurate classifiers on each subgroup separately.

    “Even when the subgroups are identified, we often do not have enough samples to train accurate classifiers on each subgroup separately.”
  • The paper relies on this without support.

    The auditor is bounded.

    “if the mistakes appear overly-complicated to the bounded auditor”
  • The authors state this as an assumption.

    A agnostic learns a class C ⊆ [-1, 1]^X of dimension d(C).

    “suppose A agnostic learns a class C ⊆ [-1, 1] X of dimension d(C).”
9 of 9

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Citations

Cites

Show all 37 references

Research works printed but not linked: 3

  1. Angwin , J. , Larson , J. , Mattu , S. , and Kirchner , L . Machine bias: There's software used across the country to predict future criminals. and it's biased against blacks. ProPublica ( 2016 ). Angwin, J., Larson, J., Mattu, S., and Kirchner, L. Machine bias: There's software used across the country to predict future criminals. and it's biased against blacks. ProPublica (2016).
  2. Chouldechova , A. , and G'Sell , M. Fairer and more accurate, but for whom? FATML ( 2016 ). Chouldechova, A., and G'Sell, M. Fairer and more accurate, but for whom? FATML (2016).
  3. Lipton , Z. C. , Wang , Y. , and Smola , A. J . Detecting and correcting for label shift with black box predictors. ICML ( 2018 ). Lipton, Z. C., Wang, Y., and Smola, A. J. Detecting and correcting for label shift with black box predictors. ICML (2018).

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Metadata

Authors
Kim, M. P., Ghorbani, A., & Zou, J.
Affiliations
Stanford University (US)
Venue
Proceedings of the 2019 AAAI/ACM Conference on AI, Ethics, and Society
Publisher
ACM
Published
2019-01-27
Pages
247-254
ISSN
3065-8365 (ISSN-L)
OpenAlex
W2962925443
Cited by
193
References
37
Citations by year
2026: 13 · 2025: 24 · 2024: 34 · 2023: 21 · 2022: 32 · 2021: 35 · 2020: 25 · 2019: 8
FWCI
25.26
Type
conference paper
Language
en
Open access
Locations
Proceedings of the AAAI/ACM Conference on AI Ethics and Society (publishedVersion, other-oa)
Funders
NSF (CCF-1763299)
Topics
  • Physical Sciences › Computer Science › Artificial Intelligence › Ethics and Social Impacts of AI
  • Physical Sciences › Computer Science › Artificial Intelligence › Explainable Artificial Intelligence (XAI)
  • Physical Sciences › Computer Science › Artificial Intelligence › Privacy-Preserving Technologies in Data
Keywords
algorithmic fairness, algorithmic auditing, post-processing, black-box access, algorithmic bias, fairness and accountability, image classification, credit scoring, population health

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