Using matched substitutes to adjust for nonignorable nonresponse: an empirical investigation using labour market data

This paper assesses the potential for reducing attrition bias by replacing survey dropouts with individuals from a refreshment sample, identified using propensity score matching. By linking administrative records with survey data, it is possible to observe outcomes for dropouts and therefore to test models of attrition. Doing so reveals the dropout process to be nonignorable such that the commonly-used method of reweighting non-dropouts is ineffective in overcoming attrition bias. By constructing artificial refreshment samples, the potential for replacing dropouts with individuals from a targeted refreshment sample is demonstrated. Where the targeting of the refreshment sample is imperfect, the success of the approach is more qualified. However, controlling for historic outcomes, the attrition bias can still be reduced.