Waiting times and socioeconomic status: does sample selection matter?

An increasing amount of empirical evidence suggests that patients with higher socioeconomic status wait less within publicly-funded hospitals to receive non-emergency (elective) surgery. Using data from Australia, we investigate the extent to which such gradient can be explained by sample selection, with richer patients being more likely to opt for treatment in the private sector when faced with waiting times in the public sector. We show that, once the potential biases introduced by sample selection are taken into account, the gradient between waiting times and socioeconomic status reduces significantly in size but does not disappear.Hospital Waiting Times; Socio-economic Gradient; Quantile regression with sample selection; Heckman model