Université de Fribourg

Bounds on direct and indirect effects under treatment/mediator endogeneity and outcome attrition

Huber, Martin ; Lafférs, Lukáš

(Working Papers SES ; 514)

Causal mediation analysis aims at disentangling a treatment effect into an indirect mechanism operating through an intermediate outcome or mediator, as well as the direct effect of the treatment on the outcome of interest. However, the evaluation of direct and indirect effects is frequently complicated by non-ignorable selection into the treatment and/or mediator, even after controlling for...

Université de Fribourg

Direct and indirect effects based on changes-in-changes

Huber, Martin ; Schelker, Mark ; Strittmatter, Anthony

(Working Papers SES ; 508)

We propose a novel approach for causal mediation analysis based on changes-in- changes assumptions restricting unobserved heterogeneity over time. This allows disentangling the causal effect of a binary treatment on a continuous outcome into an indirect effect operating through a binary intermediate variable (called mediator) and a direct effect running via other causal mechanisms. We...

Université de Fribourg

Direct and indirect effects of training vouchers for the unemployed

Huber, Martin ; Lechner, Michael ; Strittmatter, Anthony

In: Journal of the Royal Statistical Society Series A, 2018, vol. 181, no. 2, p. 441-463

This paper evaluates the effects of awarding vouchers for vocational training on the employment outcomes of unemployed voucher recipients in Germany, as well as the potential mechanism through which they operate. This study assesses the direct effects of voucher assignment net of actual redemption, which may be driven by preference shaping and learning about possible human capital investments...

Université de Fribourg

Why do tougher caseworkers increase employment? : The role of programme assignment as a causal mechanism

Huber , Martin ; Lechner, Michael ; Mellace, Giovanni

In: Review of economics and statistics, 2017, vol. 99, no. 1, p. 180-183

Previous research found that less accommodating caseworkers are more success- ful in placing unemployed workers into employment. This paper explores the causal mechanisms behind this result using semiparametric mediation analysis. Analysing rich linked jobseeker-caseworker data for Switzerland, we find that the positive employment effects of less accommodating caseworkers are not driven by a ...

Université de Fribourg

Direct and indirect effects under sample selection and outcome attrition

Huber, Martin ; Solovyeva, Anna

(Working Papers SES ; 496)

This paper considers the evaluation of direct and indirect treatment effects, also known as mediation analysis, when outcomes are only observed for a subpopulation due to sample selection or outcome attrition. For identification, we combine sequential conditional independence assumptions on the assignment of the treatment and the mediator, i.e. the variable through which the indirect effect...

Université de Fribourg

Nonparametric estimation of natural direct and indirect effects based on inverse probability weighting

Hsu, Yu-Chin ; Huber, Martin ; Lai, Tsung Chih

(Working Papers SES ; 482)

Using a sequential conditional independence assumption, this paper discusses fully nonparametric estimation of natural direct and indirect causal effects in causal mediation analysis based on inverse probability weighting. We propose estimators of the average indirect effect of a binary treatment, which operates through intermediate variables (or mediators) on the causal path between the...

Université de Fribourg

Direct and indirect effects of training vouchers for the unemployed

Huber, Martin ; Lechner, Michael ; Strittmatter, Anthony

(Working Papers SES ; 456)

This paper evaluates the effect of a voucher award system for assignment into vocational training on the employment outcomes of unemployed voucher recipients in Germany, along with the causal mechanisms through which it operates. It assesses the direct effect of voucher assignment net of actual redemption, which may be driven by preference shaping/learning about (possibilities of) human capital...

Université de Neuchâtel

Cleaner fish cause predators to reduce aggression toward bystanders at cleaning stations

Cheney, Karen L. ; Bshary, Redouan ; Grutter, Alexandra S.

In: Behavioral Ecology, 2008, vol. 19, no. 5, p. 1063-1067

Mutualisms, in which both participants gain a net benefit, are ubiquitous in all ecosystems, and the importance of understanding their broader ecological context has been demonstrated many times. Indirect effects of mutualisms may have important implications for surrounding ecosystems through changes in density, species composition, or behavior; however, the latter has been difficult to quantify....