Cited by 154Ethics and Social Impacts of AINames, Identity, and Discrimination ResearchDiscrimination and Equality Law

The problem of infra-marginality in outcome tests for discrimination

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Simoiu, Camelia, Corbett-Davies, Sam, Goel, Sharad·2017·The Annals of Applied Statistics

Abstract

Outcome tests are a popular method for detecting bias in lending, hiring, and policing decisions. These tests operate by comparing the success rate of decisions across groups. For example, if loans made to minority applicants are observed to be repaid more often than loans made to whites, it suggests that only exceptionally qualified minorities are granted loans, indicating discrimination. Outcome tests, however, are known to suffer from the problem of infra-marginality: even absent discrimination, the repayment rates for minority and white loan recipients might differ if the two groups have different risk distributions. Thus, at least in theory, outcome tests can fail to accurately detect discrimination. We develop a new statistical test of discrimination—the threshold test—that mitigates the problem of infra-marginality by jointly estimating decision thresholds and risk distributions. Applying our test to a dataset of 4.5 million police stops in North Carolina, we find that the problem of infra-marginality is more than a theoretical possibility, and can cause the outcome test to yield misleading results in practice.

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  • Thresholds cannot be identified from observed data alone, so inferences depend on the Bayesian model's functional form and prior distributions.

    “thresholds cannot be identified by the observed data alone 7 , and so inferences are dependent on the specific functional form of the underlying Bayesian model, including the prior distributions.”

    From A large-scale analysis of racial disparities in police stops across the United States (2020) · cites this paper as [7]

    Section 2.3, “Inferring search thresholds” (page unavailable), specifies a Bayesian model with priors, supporting the claim that inference uses modeling assumptions. But a passage reproduced under “Conclusion” says the model would be identified by priors rather than data *without* certain constraints; it does not say thresholds cannot be identified from observed data under the specified model. The paper also says its results are robust to the exact choice of priors, qualifying the claimed dependence on them. (LLM, conf=0.84)

    Experimental — accuracy not yet measured
  • The threshold test has been proposed as a more robust means for detecting discrimination than outcome tests.

    “the threshold test has been proposed as a more robust means for detecting discrimination 7,22 .”
  • The protected attribute is frequently represented implicitly by some combination of proxy variables, so a classifier trained without it still learns discrimination reflected in training data.

    “However, since the protected attribute is frequently represented implicitly by some combination of proxy variables, the classifier still learns the discrimination reflected in training data.”

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1 of the 30 references couldn’t be matched to a known paper.

Research works printed but not linked: 2

  1. ARROW, K. (1973). The theory of discrimination. In Discrimination in Labor Markets Princeton Univ. Press, Princeton.
  2. BECKER, G. S. (1957). The Economics of Discrimination. Univ. Chicago Press, Chicago, IL.

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Authors
Simoiu, C., Corbett-Davies, S., & Goel, S.
Affiliations
Stanford University (US)
Venue
The Annals of Applied Statistics
Published
2017-09-01
Volume
11
Issue
3
Pages
1193-1216
ISSN
  • 1932-6157 (ISSN-L)
  • 1941-7330
OpenAlex
W2950220130
Cited by
154
References
30
Citations by year
2026: 6 · 2025: 10 · 2024: 16 · 2023: 21 · 2022: 17 · 2021: 22 · 2020: 28 · 2019: 17 · 2018: 15 · 2017: 2
FWCI
38.87
Type
journal article
Language
en
Open access
Locations
  • The Annals of Applied Statistics (publishedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • Project Euclid (Cornell University) (submittedVersion)
  • arXiv (Cornell University)
Funders
Stanford Bio-X
Topics
  • Social Sciences › Safety Research › Ethics and Social Impacts of AI
  • Social Sciences › Sociology and Political Science › Names, Identity, and Discrimination Research
  • Social Sciences › Law › Discrimination and Equality Law
Keywords
discrimination detection, threshold test, decision threshold, risk allocation, algorithmic fairness, police stops, racial disparities, loan repayment rates, hiring discrimination, credit discrimination

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