After adjustment for baseline sewerage coverage and other confounding variables (such as education and type of housing), it was found that diarrhoea prevalence fell on average by 22% (from 9.2 days per child-year before the intervention to 7.3 afterwards) and by 42% in areas with high prevalence of diarrhoea prior to the intervention. Most of this reduction was explained by the increased coverage of the sewerage system that has been constructed during the intervention. The intervention had an even bigger impact on other diseases, According Shankland et al.,