This is very interesting work with substantial policy relevance. One question: while it makes sense that having access to increasing numbers of the drivers has an increasingly positive association with lower stunting rates, were you able to determine whether the whole is greater than the sum of the parts? - i.e. is their a positive interaction effect, whereby (say) having access to improved food security and improved WASH has a bigger combined impact than just the impact you get from improving each individually?
Given limited resources and the need to scale up many different interventions in different sectors in different geographies, it would be helpful to understand if there are positive (or conceivably negative) interactions associated with scaling up some combinations in the same geography. e.g. we may not get the full benefits from improved food if we don't reduce diarrheal disease and loss of nutrients; conversely, increasing exclusive breastfeeding rates may have less marginal benefit in areas with improved water quality compared with areas with poor water quality, if part of the benefit of exclusive breastfeeding is avoiding contaminated baby formula and water-borne disease.
Clearly the eventual goal should be strong programs across all sectors in all places, but until we get there there may be better and worse ways of deploying scarce resources for the scale up. Would love to hear any insights on this from your work.