junctures such as after defecation. We also find small but significant improvements from handwashing promotion along other indicators of cleanliness including the child’s state of cleanliness, caregiver’s hands, probability of covering food and cleaning of the household latrine. Intermediate outcomes in the combined handwashing and sanitation intervention are consistent with impacts found in the single intervention wards. We find no clear evidence of meaningful health impacts. On the one hand, using 34,045 child observations from the listing data, we find a marginally significant (12.5%) reduction in diarrhea,<sup>7</sup> particularly for children under three in the combined treatment wards, pointing towards potential complementarities. The household survey data of 5,768 children shows a statistically insignificant reduction. Counterintuitively, we also find small but significant reductions in hemoglobin levels measuring iron-deficiency anemia (1.5%) and weight-for-age in the combination ward, which could be driven by gut infections and soil-transmitted helminthes (STHs) reducing the body’s ability to absorb nutrients. These anemia and weight results are statistically significant but biologically small. We show that this counterintuitive result is unlikely to be driven by selective mortality or poor quality latrine construction and the results remain robust to a number of different specifications.

The study design presents some limitations which we mention upfront. First, the 10 districts where we conduct the study were selected by government based on political priority rather than random selection, affecting the external validity of the study. This said, comparing our control group to representative surveys of rural Tanzania, including the 2010 Demographic and Health Survey and National Panel Survey, reveals that the two areas are more similar than not along basic observable characteristics (refer to Table 1). Since these are predominantly rural households, we also find that our sample is poorer on average than the national population. Following Filmer and Pritchett (2001), we use principal-components analysis to derive a wealth index based on 16 household assets captured both in the study questionnaire and the nationally representative 2010-2011 Living Standards Measurement Survey (LSMS). By plotting the wealth distributions of the impact evaluation and LSMS samples, Figure 1 shows that approximately 57% of the impact evaluation group falls below the 40<sup>th</sup> percentile of the national wealth distribution – the target group for the World Bank’s goal of increasing shared prosperity.

The second important concern is that we lack a baseline of pre-intervention characteristics.<sup>8</sup> While we attempt to reconstruct baselines for key variables, these suffer from problems of recall. Differential migration and attrition could also be a concern. However, data from the complete census listings of selected enumerator areas provides evidence of limited migration and attrition. Less than 5% of households moved into the community within the three year intervention period,

> 7 The household-level indicator for diarrhea including 5768 households does not find any significant effect on diarrhea, although the direction of the sign for the coefficient is consistent.

> 8 Although a baseline data collection was intended, unanticipated problems with reliability of data resulted in the cancelation of field work in five out of the 10 districts originally planned and the impossibility of using the data to validate the randomized design, as it was originally planned.

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