Matching Estimators

Matching is a widely used non-experimental method of evaluation that can be used to estimate the average effect of a treatment or programme intervention. The method compares the outcomes of programme participants with those of matched non-participants, where matches are chosen on the basis of similarity in observed characteristics. One of the main advantages of matching estimators is that they typically do not require specifying the functional form of the outcome equation and are therefore not susceptible to misspecification bias along that dimension. Traditional matching estimators pair each programme participant with a single matched non-participant (see, for example, Rosenbaum and Rubin, 1983), whereas more recently developed estimators pair programme participants with multiple non-participants and use weighted averaging to construct the matched outcomes.