Causal decomposition analysis with synergistic interventions: A triply robust machine-learning approach to addressing...

Educational disparities are rooted in, and perpetuate, social inequalities across multiple dimensions such as race, socioeconomic status, and geography. To reduce disparities, most intervention strategies focus on a single domain and frequently evaluate their effectiveness by using causal decomposition analysis. However, a growing body of research suggests that single-domain interventions may be insufficient for individuals marginalized on multiple fronts. While interventions across multiple domains are increasingly proposed, there is limited guidance on appropriate methods for evaluating their effectiveness. To address this gap, we develop an extended causal decomposition analysis that simultaneously targets multiple causally ordered intervening factors, allowing for the assessment of their synergistic effects. These scenarios often involve challenges related to model misspecification because of complex interactions among group categories, intervening factors, and their confounders with the outcome. To mitigate these challenges, we introduce a triply robust estimator that leverages machine-learning techniques to address potential model misspecification. We apply our method to a cohort of students from the High School Longitudinal Study (HSLS:09), focusing on math achievement disparities between Black, Hispanic, and White high schoolers. Specifically, we examine how two sequential interventions-equalizing the proportion of students who attend high-performing schools and equalizing enrollment in Algebra I by ninth grade across racial groups-may reduce these disparities. (PsycInfo Database Record (c) 2026 APA, all rights reserved).