Hong, G., & Nomi, T. (2012). Weighting methods for assessing policy effects mediated by peer change.

By applying a new weighting procedure, we estimate the average potential outcome if the entire population were treated, the average potential outcome if the entire population were untreated, and the average potential outcome if the entire population were treated and if every individual unit’s mediator value would counterfactually remain at the same level as it would be when untreated. The estimated differences among these average potential outcomes provide estimates of the total effect, the natural direct effect, and the natural indirect effect. This alternative approach avoids some strong identification assumptions invoked by the conventional approaches.

Hong, G., & Nomi, T. (2012). Weighting methods for assessing policy effects mediated by peer change. Journal of Research on Educational Effectiveness special issue on the statistical approaches to studying mediator effects in education research, 5(3), 261-289.