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Common Functional Decompositions Can Mis-attribute Differences in Outcomes Between Populations

Manuel Quintero, William T. Stephenson, Advik Shreekumar, Tamara Broderick

arXiv 23 Apr 2025 · Statistics — Methodology

arXiv:2504.16864 · PDF · DOI · OpenAlex · Extracted main text

Abstract

In science and social science, we often wish to explain why an outcome is different in two populations. For instance, if a jobs program benefits members of one city more than another, is that due to differences in program participants (particular covariates) or the local labor markets (outcomes given covariates)? The Kitagawa-Oaxaca-Blinder (KOB) decomposition is a standard tool in econometrics that explains the difference in the mean outcome across two populations. However, the KOB decomposition assumes a linear relationship between covariates and outcomes, while the true relationship may be meaningfully nonlinear. Modern machine learning boasts a variety of nonlinear functional decompositions for the relationship between outcomes and covariates in one population. It seems natural to extend the KOB decomposition using these functional decompositions. We observe that a successful extension should not attribute the differences to covariates -- or, respectively, to outcomes given covariates -- if those are the same in the two populations. Unfortunately, we demonstrate that, even in simple examples, two common decompositions -- functional ANOVA and Accumulated Local Effects -- can attribute differences to outcomes given covariates, even when they are identical in two populations. We provide a characterization of when functional ANOVA misattributes, as well as a general property that any discrete decomposition must satisfy to avoid misattribution. We show that if the decomposition is independent of its input distribution, it does not misattribute. We further conjecture that misattribution arises in any reasonable additive decomposition that depends on the distribution of the covariates.

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31
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43
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31
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Most heavily cited references

The works this paper leans on most, across its whole bibliography — not restricted to papers in our corpus. Ranked by composite intensity, which combines how often a work is mentioned, how many sections mention it, and how much of that falls in the main text rather than the appendix.

ReferenceIntensityMentionsSectionsMain text
1Daniel W. Apley and Jingyu Zhu (2020) Visualizing the effects of predictor variables in black box supervised learning models0.92843100%
2Giles Hooker (2007) Generalized Functional ANOVA Diagnostics for High-Dimensional Functions of Dependent Variables0.8434475%
3Giles Hooker (2004) Discovering additive structure in black box functions0.84333100%
4Raj Agrawal and Tamara Broderick (2023) The skim-fa kernel: high-dimensional variable selection and nonlinear interaction discovery in linear time self0.40511100%
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6Philipp Bach, Victor Chernozhukov, and Martin Spindler (2024) Heterogeneity in the us gender wage gap0.40511100%
7Amine Belhadi, Swapnil S. Kamble, V. Mani, et al (2021) An ensemble machine learning approach for forecasting credit risk of agricultural smes’ investments in agriculture 4.0 through s…0.40511100%
8Alan S. Blinder (1973) Wage Discrimination: Reduced Form and Structural Estimates0.40511100%
9Gaelle Chastaing, Fabrice Gamboa, and Clémentine Prieur (2012) Generalized Hoeffding-Sobol decomposition for dependent variables - application to sensitivity analysis0.40511100%
10Nicole Fortin, Thomas Lemieux, and Sergio Firpo (2011) Decomposition Methods in Economics0.40511100%

Showing the top 10 of 31 scored citations.

Cited by, within the corpus

arXiv econ.EM papers that cite this one, ranked by how heavily they lean on it.

Citing paperIntensityMentionsSections
1Do covariates explain why these groups differ? The choice of reference group can reverse conclusions in the Oaxaca-Blinder decomposition0.64422