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

This paper discusses the nonparametric 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 using distinct...

Université de Fribourg

A simple test for the ignorability of non-compliance in experiments

Huber, Martin

In: Economics letters, 2013, vol. 120, no. 3, p. 389-391

This paper proposes a simple method for testing whether non-compliance in experiments is ignorable, i.e., not jointly related to the treatment and the outcome. The approach consists of (i) regressing the outcome variable on a constant, the treatment, the assignment indicator, and the treatment/assignment interaction and (ii) testing whether the coefficients on the latter two variables are...

Université de Fribourg

Sensitivity checks for the local average treatment effect

Huber, Martin Huber

In: Economics letters, 2014, vol. 123, no. 2, p. 220-223

The nonparametric identification of the local average treatment effect (LATE) hinges on the satisfaction of three instrumental variable assumptions: (1) Unconfounded assignment of the instrument, (2) no average direct effect of the instrument on the outcome within compliance types (exclusion restric- tion), and (3) weak monotonicity of the treatment in the instrument. While (1) often appears...

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...

Université de Fribourg

Testing the validity of the sibling sex ratio instrument

Huber, Martin

In: Labour, 2015, vol. 29, no. 1, p. 1-14

We test the validity of the sibling sex ratio instrument in Angrist and Evans (1998) using the methods proposed by Kitagawa (2008) and Huber and Mellace (2014). The sex ratio of the first two siblings is arguably randomly assigned and influences the probability of having a third child, which makes it a candidate instrument for fertility when estimating the effect of fertility on female labor...

Université de Fribourg

The Effect of Firms' Phased Retirement Policies on the Labor Market Outcomes of Their Employees

Huber, Martin ; Lechner, Michael ; Wunsch, Conny

In: ILR review, 2016, vol. 69, no. 5, p. 1216-1248

In this article, the authors assess the impact of firms’ offering a special form of phased retirement on their male employees’ labor market outcomes. The program aims at smoothing the transition from work to retirement and at decreasing costs in the public pension and unemployment insurance schemes through an increase in employment of elderly workers who otherwise would have exited...

Université de Fribourg

Direct and indirect effects based on difference-in-differences with an application to political preferences following the Vietnam draft lottery

Deuchert, Eva ; Huber, Martin ; Schelker, Mark

(Working Papers SES ; 473 (revised))

This paper proposes a difference-in-differences approach for disentangling a total treatment effect on some outcome into a direct effect as well as an indirect effect operating through a binary intermediate variable – or mediator – within strata defined upon how the mediator reacts to the treatment. Imposing random treatment assignment along with specific common trend (and further)...

Université de Fribourg

Testing the validity of the compulsory schooling law instrument

Bolzern, Benjamin ; Huber, Martin

(Working Papers SES ; 480)

Changes in compulsory schooling laws have been proposed as an instrument for the endogenous choice of schooling. It has been argued that raising minimum schooling exogenously increases the educational attainment of a subset of pupils without directly affecting later life outcomes such as income or health. Using the method of Huber and Mellace (2015) and data from the Survey of Health, Ageing and...

Université de Fribourg

Evaluating local average and quantile treatment effects under endogeneity based on instruments : a review

Huber, Martin ; Wüthrich, Kaspar

(Working Papers SES ; 479)

This paper provides a review of methodological advancements in the evaluation of heterogeneous treatment effect models based on instrumental variable (IV) methods. We focus on models that achieve identification through a monotonicity assumption on the selection equation and analyze local average and quantile treatment effects for the subpopulation of compliers. We start with a comprehensive...

Université de Fribourg

Direct and indirect effects based on difference-in-differences with an application to political preferences following the Vietnam draft lottery

Deuchert, Eva ; Huber, Martin ; Schelker, Mark

(Working Papers SES ; 473)

This study empirically evaluates the impact of the war in eastern Ukraine on the political attitudes aThis paper proposes a difference-in-differences approach for disentangling a total treatment effect on some outcome into a direct impact as well as an indirect effect operating through a binary intermediate variable – or mediator – within strata defined upon how the mediator reacts to the...