This guide reports that to date there have been few or no rigorous scientific impact evaluations showing that water supply and sanitation policies are effective in delivering desired outcomes, except for health. It argues that a rigorous scientific impact evaluation must utilise some mix of control groups, baselines, and covariates to establish the counterfactual scenario and permit the estimation of impacts. A review of the literature suggests that there are essentially three sets of completed studies and a few other on-going evaluations that have evaluated the impacts of water supply and sanitation policies, including privatisation, decentralised delivery, and information campaigns. The report speculates on possible reasons for the lack of rigorous evaluations in the sector.
