Université de Fribourg

Direct and indirect treatment effects - causal chains and mediation analysis with instrumental variables

Fröhlich, Markus ; Huber, Martin

In: Journal of the Royal Statistical Society Series B, 2017, vol. 79, no. 5, p. 1645-1666

The paper discusses the non‐parametric identification of causal direct and indirect effects of a binary treatment based on instrumental variables. We identify the indirect effect, which operates through a mediator (i.e. intermediate variable) that is situated on the causal path between the treatment and the outcome, as well as the unmediated direct effect of the treatment by using distinct...

Université de Fribourg

Sharp IV bounds on average treatment effects on the treated and other populations under endogeneity and noncompliance

Huber, Martin ; Laffers, Lukas ; Mellace, Giovanni

In: Journal of Applied Econometrics, 2017, vol. 32, no. 1, p. 56-79

In the presence of an endogenous binary treatment and a valid binary instru- ment, causal effects are point identified only for the subpopulation of compliers, given that the treatment is monotone in the instrument. With the exception of the entire population, causal inference for further subpopulations has been widely ignored in econometrics. We invoke treatment monotonicity and/or dominance...

Université de Fribourg

Testing instrument validity for LATE identification based on inequality moment constraints

Huber, Martin ; Mellace, Giovanni

In: Review of economics and statistics, 2015, vol. 97, no. 2, p. 398-411

We derive testable implications of instrument validity in just identified treat- ment effect models with endogeneity and consider several tests. The identifying assump- tions of the local average treatment effect allow us to both point identify and bound the mean potential outcomes (i) of the always takers under treatment and (ii) of the never takers under non-treatment. The point identified...