Causal Inference with the "Napkin Graph"

Fuente: arXiv
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Main Authors: Guo, Anna, Benkeser, David, Nabi, Razieh
Format: Preprint
Published: 2025
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author Guo, Anna
Benkeser, David
Nabi, Razieh
author_facet Guo, Anna
Benkeser, David
Nabi, Razieh
contents Unmeasured confounding can render identification strategies based on adjustment functionals invalid. We study the "Napkin graph", a causal structure that encapsulates patterns of M-bias, instrumental variables, and the classical back-door and front-door models within a single graphical framework, yet requires a nonstandard identification strategy: the average treatment effect is expressed as a ratio of two g-formulas. We develop novel estimators for this functional, including doubly robust one-step and targeted minimum loss-based estimators that remain asymptotically linear when nuisance functions are estimated at slower-than-parametric rates using machine learning. We also show how a generalized independence restriction encoded by the Napkin graph, known as a Verma constraint, can be exploited to improve efficiency, illustrating more generally how such constraints in hidden variable DAGs can inform semiparametric inference. The proposed methods are validated through simulations and applied to the Finnish Life Course study to estimate the effect of educational attainment on income. An accompanying R package, napkincausal, implements all proposed procedures.
format Preprint
id arxiv_https___arxiv_org_abs_2512_19861
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Causal Inference with the "Napkin Graph"
Guo, Anna
Benkeser, David
Nabi, Razieh
Methodology
Machine Learning
Unmeasured confounding can render identification strategies based on adjustment functionals invalid. We study the "Napkin graph", a causal structure that encapsulates patterns of M-bias, instrumental variables, and the classical back-door and front-door models within a single graphical framework, yet requires a nonstandard identification strategy: the average treatment effect is expressed as a ratio of two g-formulas. We develop novel estimators for this functional, including doubly robust one-step and targeted minimum loss-based estimators that remain asymptotically linear when nuisance functions are estimated at slower-than-parametric rates using machine learning. We also show how a generalized independence restriction encoded by the Napkin graph, known as a Verma constraint, can be exploited to improve efficiency, illustrating more generally how such constraints in hidden variable DAGs can inform semiparametric inference. The proposed methods are validated through simulations and applied to the Finnish Life Course study to estimate the effect of educational attainment on income. An accompanying R package, napkincausal, implements all proposed procedures.
title Causal Inference with the "Napkin Graph"
topic Methodology
Machine Learning
url https://arxiv.org/abs/2512.19861