Table 6.

Summary of inclusion criteria

Criteria	Definition
Populations	Human populations in LMICs, as defined by the World Bank at the time the research was carried out. Populations of any age, sex, gender, disability or socioeconomic status were included. Populations in epidemics (e.g., cholera outbreak) were excluded
Interventions	Demand‐side (behaviour change communication, subsidies, microloans, legal measures), supply‐side (direct hardware provision, privatisation and nationalisation, small‐scale independent provider involvement, improved operator performance), or combinations of demand and/or supply (e.g., decentralisation)
	Technology and place of use: water supply, water quality, sanitation, and/or hygiene in the household, community, school or health facility
Comparators	Impact evaluations where the comparison/control group receives no intervention (standard WASH access), a different WASH intervention, a double‐blind placebo (e.g., nonfunctioning water filter), a single‐blind (e.g., school textbooks), or a pipeline (wait‐list)
Outcomes	Behaviour, health, and socioeconomic outcomes. Studies that only reported measures of knowledge or attitudes were excluded. WTP was included where based on real purchase decisions
Study design	Randomised controlled trials, prospective and retrospective nonrandomised studies, natural experiments, and systematic reviews. For time use outcomes only: the above plus reflexive controls. For mortality outcomes only: the above plus case‐control designs
Language	Studies in English, French, Spanish and Portuguese. Studies in other languages were included where an English translation was available
Time frame	No study was excluded based on date of publication

Abbreviations: LMIC, low‐ and middle‐income country; WTP, willingness‐to‐pay.