A systematic review [1] investigated the effect of private-sector participation (PSP) on infrastructure, including access to and quality of water supply. Of the outcomes listed, 70% were positive; around two-thirds were positive in relation to access and service quality, and slightly fewer for product quality. However, most of the studies were qualitative, and these produced more positive reports (84%) than the quantitative studies (40%). In relation to infrastructure overall, the review found that:

• PSP on its own does not seem to have a significant impact on improvements in access and quality
• Without financial support from the government, access to poor and rural consumers are affected as a result of PSP
• Clearly identifying the objectives of PSP would help in appropriately handling the potential trade-offs between outcomes.

A systematic review of water, sanitation and hygiene (WASH) initiatives found the following [2]:

• Post-intervention sustainability is often measured by a combination of survey, interview and observation. There is no clear definition for sustained adoption employed in WASH literature, and sustained adoption is measured through self-report, observed practice, functionality and recalled knowledge.
• Behavioural factors that influence sustained adoption:
  • Psychosocial factors: Perceived susceptibility and severity of disease and perceived benefits and barriers are commonly identified as influences on sustained adoption. However, some other factors, such as injunctive and descriptive norms and nurturing, may be more predictive as motivators of continued use over time.
  • Contextual factors: Age and gender are important factors that influence both who is able to practise the behaviour at the household level, and to determine roles in providing water, soap and child care.
  • Technology factors: Cost is an important factor regardless of the technology. Factors like durability, rate of water flow and maintenance are key in ensuring that technologies withstand frequent use over a long period of time.
• Programme characteristics influencing sustained adoption:
  • Communication strategies were the most commonly described. The most influential factors include frequent, personal contact with a health promoter over a period of time. Personal follow-up in conjunction with on-going communication and support through mass media advertisements or group meetings may further contribute to sustained adoption.

A third systematic review [3] examined the effectiveness of different urban planning approaches on providing access to water and sanitation services in low-income or informal settlements in low- and middle-income countries:

• Services provided by public or private agencies through centralised planning and implementation (top-down) appeared effective in individual studies, but this was not confirmed by statistical meta-analysis. Qualitative synthesis of contextual factors suggest a need for the customisation of solutions to meet local needs, and better delivery of services by alternative/non-government service providers.
• In relation to toilets, participatory (bottom-up) approaches adopted by NGOs and CBOs suit the construction and maintenance of toilets, which can be standalone; statistical meta-analysis confirms their effectiveness for individual but not community toilets.
• Although studies of bottom-up approaches to improving water access appeared positive more often than studies of top-down approaches, this difference was not statistically significant in a meta-analysis. Moreover, bottom-up approaches suffer from problems of scaling-up.
• Replication of successful models may not always be possible, since the same conditions may not be present in different locations.
• Neighbourhoods without security of tenure are rarely served well top-down. Bottom-up approaches are also limited in this context, and also in Africa, where efforts may be hampered by particularly modest levels of economic development.
• Public-private partnership model, with built in pro-poor contractual features and institutional flexibility, can serve as an effective mechanism for improved water-supply services. Bottom-up, NGO-led initiatives for improving water supply need the co-operation and support of the public sector.

1. Impact of private-sector involvement on access and quality of service in electricity, telecom, and water supply sectors: a systematic review of the evidence in developing countries (2013)

2. What factors affect sustained adoption of safe water, hygiene and sanitation technologies? A systematic review of literature (2015)

3. What is the evidence on top-down and bottom-up approaches in improving access to water, sanitation and electricity services in  low-income or informal settlements? (2016)