Identifying causal mechanisms in experiments (primarily) based on inverse probability weighting

Martin Huber

No 1213, Economics Working Paper Series from University of St. Gallen, School of Economics and Political Science

Abstract: This paper demonstrates the identification of causal mechanisms in experiments with a binary treatment, (primarily) based on inverse probability weighting. I.e., we consider the average indirect effect of the treatment, which operates through an intermediate variable (or mediator) that is situated on the causal path between the treatment and the outcome, as well as the (unmediated) direct effect. Even under random treatment assignment, subsequent selection into the mediator is generally non-random such that causal mechanisms are only identified when controlling for confounders of the mediator and the outcome. To tackle this issue, units are weighted by the inverse of their conditional treatment propensity given the mediator and observed confounders. We show that the form and applicability of weighting depend on whether the confounders are themselves influenced by the treatment or not. A simulation study gives the intuition for these results and an empirical application to the direct and indirect health effects (through employment) of the U.S. Job Corps program is also provided.

Keywords: Causal mechanisms; mediation analysis; direct and indirect effects; experiment; inverse probability weighting (search for similar items in EconPapers)
JEL-codes: C14 C21 I38 (search for similar items in EconPapers)
Pages: 40 pages
Date: 2012-05, Revised 2013-05
New Economics Papers: this item is included in nep-ecm
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Citations: View citations in EconPapers (16)

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Persistent link: https://EconPapers.repec.org/RePEc:usg:econwp:2012:13

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