Health Research and Policy

Research in Progress Seminar (RIP)

Date: March 5, 2014
Time: 4:00 - 5:00 pm
Location: CHP/PCOR Conference Room
117 Encina Commons
Speaker: A. David Paltiel
Yale School of Public Health & Yale School of Management
Title: Reducing Sexual Violence by Increasing the Supply of Toilets in Khayelitsha, South Africa: A Mathematical Model


This is joint work with Gregg S Gonsalves, Edward H Kaplan, A David Paltiel.

Background: Sexual violence is a major public health issue, affecting 35% of women worldwide. Major risk factors for sexual assault include inadequate indoor sanitation and the need to travel to outdoor toilet facilities. We estimated how increasing the number of toilets in an urban township (Khayelitsha, South Africa) might reduce both economic costs and the incidence and social burden of sexual assault.

Methods: We developed a mathematical model that links risk of sexual assault to the number of sanitation facilities and the time a woman must spend walking to a toilet. We defined a composite societal cost function, comprising both the burden of sexual assault and the costs of installing and maintaining public chemical toilets. By expressing total social costs as a function of the number of available toilets, we were able to identify an optimal (i.e., cost-minimizing) social investment in toilet facilities.

Findings: There are currently 5600 toilets in Khayelitsha. This results in 635 sexual assaults and US$40 million in combined social costs each year. Increasing the number of toilets to 11300 would minimize total costs ($35 million) and reduce sexual assaults to 446. Higher toilet installation and maintenance costs would be more than offset by lower sexual assault costs. Sensitivity analysis shows that in every deviation from base case assumptions, the optimal number of toilets significantly exceeds the original allocation of toilets in the township.

Interpretation: Improving access to sanitation facilities in urban settlements will simultaneously reduce the incidence of sexual assaults and overall cost to society. Since our analysis ignores the many additional health benefits of improving sanitation in resource-constrained urban areas (e.g., potential reductions in waterborne infectious diseases), the optimal number of toilets identified here should be interpreted as conservative.

Please note: All research in progress seminars are off-the-record. Any information about methodology/press release and/or results are embargoed until publication.
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