People are dying from a lack of clean water. In fact it is the leading cause of death in Africa. One point eight million people die each year from waterborne illnesses. Of those, one million are children. Clean water can prevent legions of child health problems and dramatically reduce infant mortality. Scientific evidence is overwhelmingly positive on impact. A World Health Organization study estimates that the availability of clean water in a rural village reduces infant mortality by 35 to 50 percent, at a cost of roughly $10 per person per year. Because infant mortality rates in the poorest countries often range from 60 to 110 per 1,000 live births, the cost of saving a child's life by providing clean water alone may lie in the range of only $180 to $400. To development economists, cheap-plus-effective is an endearing combination.