In rural Bangladesh, when free-of cost WASH technologies were provided alongwith behavior change promotion, poorer households exhibited the greatest improvement in handwashing and sanitation uptake compared with wealthier households. This finding is consistent to results found in a non-randomized trial in rural Bangladesh, where households with the highest handwashing uptake, as evidenced by presence of low-cost soap alternative, were the ones that received handwashing promotion along with some sort of products and equipment support versus households that received handwashing promotion only (47).
The least educated households in the current study also exhibited greater improvements in handwashing and sanitation uptake compared with more educated households. This suggests that education level was less important for uptake of these preventive interventions, than lack of access to appropriate hardware and encouragement to use the hardware.
At baseline for both intervention and control groups, the poorest and the groups with the least education had the lowest levels of sanitation and handwashing behaviors and the wealthiest already had relatively higher levels. This distribution is typical for WASH indicators. The poorest and least educated improved the most because they also had the greatest scope for improvement. This pattern is also found in program context— communities with lowest levels of sanitation coverage have the highest improvements, while communities with already high baseline levels of coverage improve the least (27, 48). Regardless of the degree of improvement over the intervention period for each wealth and education level, the final uptake rates for all wealth and education levels were high. These final uptake levels are higher than handwashing prevalence and latrine use rates recorded in most other handwashing and sanitation interventions reviews (48, 49).
Strengthening the supply-side of an intervention means ensuring access to appropriate hardware such as handwashing stations and durable and functional latrines. In Bangladesh, having a permanent designated handwashing place with soap and water present at that location, was associated with increased handwashing practices independent of socioeconomic status (13). Furthermore, in many program contexts easy access to hardware does not negatively affect usage. In Zambia, people who paid lower prices for point-of-use water treatment solution were not less likely to use it relative to people who paid higher prices (50). Similarly, in Kenya, women who received free bednets were equally likely to use them as women who paid for bednets (51).
Uptake is adversely affected when hardware support is suboptimal and scaled-up demand-driven or supply-driven programs are unable to ensure high quality infrastructure. Programs like CLTS may have improved coverage, but improved coverage may not equate to improved levels of usage in the context of large-scale programs (48). The poorest commonly revert back to open defecation due to low-quality sanitation structures that are prone to collapse, or fill with no provision for emptying (52–54). Many latrines built as part of CLTS are unimproved and shared; they do not effectively remove waste from the environment and are not sustainable (55).
In settings where the poorest lack financial resources to access health improving hardware, addressing supply constraints through free provision can support a pro-equity impact. However, free distribution may not always be possible and so subsidies (56–59) are one way of alleviating supply constraints and increasing demand among the poorest in scaled-up contexts. Subsidies or free provision of hardware can help the poorest move up the sanitation ladder (55). CLTS programs are increasingly exploring potential of financing mechanisms in order to reach the poorest and most marginalized (53, 54). An experimental study conducted in Bangladesh compared hygienic latrine ownership between landless poor who were provided community motivation alone, supply-side market intervention alone, and subsidies (60). The group that was provided subsidies increased latrine ownership the most.
Strengthening the supply side of an intervention should not come at the cost of a weak approach to demand generation. Ensuring access to appropriate WASH hardware is a necessary, but generally not sufficient condition for uptake among the poorest. Behavior change promotion is also important to ensure continued use and habit formation for WASH behaviors.
There are important limitations to the conclusions that we can draw from this analysis. First, the study design does not allow us to specify which component of the WASH Benefits intervention design, the behavior-change promotional activities or the WASH hardware provision, was more important to address equity. Although this is likely to vary by context, future studies could deploy experimental methods with varying levels of demand and supply-side components to understand which strategy would be most cost-effective in order to achieve equitable impact.
A second limitation is that the current analysis examined wealth and education inequity only. However, considerations of inequity outside the controlled setting of a randomized controlled trial may also affect communities including geographical, ethnic and gender inequity (61).
Finally, the WASH Benefits Bangladesh intervention occurred as part of an intensive scientific study with focused effort to maximize uptake. It is unclear whether interventions with the intensity typical of WASH programs could generate similar pro equity results. High level of CHP engagement in smaller clusters, and free or heavily subsidized provision of hardware to all participants are not scalable in most circumstances. Within scaled-up programs, one possible approach could be to have two distinct strategies—one focused on efficiency to reach the highest number of program beneficiaries, and a separate dedicated strategy for the poorest that can mimic the conditions of an efficacy trial. Such as approach has been employed by BRAC WASH program, where all participants received sanitation promotion, but the ultra poor are provided free latrines once 80% coverage is reached in a community, and in areas where coverage is less than 80%, the poor and ultra poor are provided with subsidies (62). Such a strategy is likely to be more effective in terms of improving equity of a program.