Optimising Balance Using Covariate Balancing Propensity Score: The Case of South African Child Support Grant

In this paper, we explore the use of covariate balancing propensity scores (CBPS) in estimating the impact of the South African child support grant (CSG) on the height-for-age score of benefiting children. CBPS is a different approach to estimating propensity score, under CBPS the scores are estimated such that the estimation incorporates covariate balancing condition. This approach is therefore relatively robust to misspecification of the propensity score model which makes it ideal for this case study. We show that utilising the CBPS leads to treatment effect estimate that is larger and more precisely estimated than estimates that have been reported in the literature because the method exploits the dual function of propensity score. The effect of CSG under CBPS is as large as 44% of standard deviation on average. This implies that the effect of the grant cannot be regarded as small as previously reported in the literature.