Combining Matching and Nonparametric IV Estimation: Theory and an Application to the Evaluation of Active Labour Market Policies

In this paper, we show how instrumental variable and matching estimators can be combined in order to identify a broader array of treatment effects. Instrumental variable estimators are known to estimate effects only for the compliers, which often represent only a small subset of the entire population. By combining IV with matching, we can estimate also the treatment effects for the always- and never-takers. In our application to the active labour market programmes in Switzerland, we find large positive employment effects for at least 8 years after treatment for the compliers. On the other hand, the effects for the always- and never-participants are small. In addition, when examining the potential outcomes separately, we find that the compliers have the worst employment outcomes without treatment. Hence, the assignment policy of the caseworkers was inefficient in that the always-participants were neither those with the highest treatment effect nor those with the largest need for assistance.