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Summary In many observational studies, the treatment assignment mechanism is not individualistic, as it allows the probability of treatment of a unit to depend on quantities beyond the unit’s covariates. In such settings, unit treatments may be entangled in complex ways. In this article, we consider a particular instance of this problem where the treatments are entangled by a social network among units. For instance, when studying the effects of peer interaction on a social media platform, the treatment on a unit depends on the change of the interactions network over time. A similar situation is encountered in many economic studies, such as those examining the effects of bilateral trade partnerships on countries’ economic growth. The challenge in these settings is that individual treatments depend on a global network that may change in a way that is endogenous and cannot be manipulated experimentally. In this paper, we show that classical propensity score methods that ignore entanglement may lead to large bias and wrong inference of causal effects. We then propose a solution that involves calculating propensity scores by marginalizing over the network change. Under an appropriate ignorability assumption, this leads to unbiased estimates of the treatment effect of interest. We also develop a randomization-based inference procedure that takes entanglement into account. Under general conditions on network change, this procedure can deliver valid inference without explicitly modelling the network. We establish theoretical results for the proposed methods and illustrate their behaviour via simulation studies based on real-world network data. We also revisit a large-scale observational dataset on contagion of online user behaviour, showing that ignoring entanglement may inflate estimates of peer influence.
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A Look into Causal Effects under Entangled Treatment in Graphs: Investigating the Impact of Contact on MRSA Infection
Methicillin-resistant Staphylococcus aureus (MRSA) is a type of bacteria resistant to certain antibiotics, making it difficult to prevent MRSA infections. Among decades of efforts to conquer infectious diseases caused by MRSA, many studies have been proposed to estimate the causal effects of close contact (treatment) on MRSA infection (outcome) from observational data. In this problem, the treatment assignment mechanism plays a key role as it determines the patterns of missing counterfactuals --- the fundamental challenge of causal effect estimation. Most existing observational studies for causal effect learning assume that the treatment is assigned individually for each unit. However, on many occasions, the treatments are pairwisely assigned for units that are connected in graphs, i.e., the treatments of different units are entangled. Neglecting the entangled treatments can impede the causal effect estimation. In this paper, we study the problem of causal effect estimation with treatment entangled in a graph. Despite a few explorations for entangled treatments, this problem still remains challenging due to the following challenges: (1) the entanglement brings difficulties in modeling and leveraging the unknown treatment assignment mechanism; (2) there may exist hidden confounders which lead to confounding biases in causal effect estimation; (3) the observational data is often time-varying. To tackle these challenges, we propose a novel method NEAT, which explicitly leverages the graph structure to model the treatment assignment mechanism, and mitigates confounding biases based on the treatment assignment modeling. We also extend our method into a dynamic setting to handle time-varying observational data. Experiments on both synthetic datasets and a real-world MRSA dataset validate the effectiveness of the proposed method, and provide insights for future applications.
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- PAR ID:
- 10434603
- Publisher / Repository:
- ACM
- Date Published:
- ISBN:
- 9798400701030
- Format(s):
- Medium: X
- Location:
- Long Beach CA USA
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1145/3580305.3599763
