Sustainable and equitable access to safe water and adequate sanitation are widely acknowledged as vital, yet neglected, development goals. Water supply and sanitation (WSS) policies are justified because of the usual efficiency criteria, but also major equity concerns. Yet, to date there are few scientific impact evaluations showing that WSS policies are effective in delivering social welfare outcomes. This lack of an evaluation culture is partly because WSS policies are characterized by diverse mechanisms, broad goals and the increasing importance of decentralized delivery, and partly because programme administrators are unaware of appropriate methods. We describe a protocol for a quasi-experimental evaluation of a community-demand-driven programme for water and sanitation in rural India, which addresses several evaluation challenges. After briefly reviewing policy and implementation issues in the sector, we describe key features of our protocol, including control group identification, pre-post measurement, programme theory, sample sufficiency and robust indicators. At its core, our protocol proposes to combine propensity score matching and difference-in-difference estimation. We conclude by briefly summarizing how quasi-experimental impact evaluations can address key issues in WSS policy design and when such evaluations are needed.

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