Michael Kremer and his colleagues came up with one method: a (free) chlorine dispenser, called “one turn,” installed next to the village well, where everybody goes to get water, which delivers the right quantity of chlorine at one turn of a knob. This makes the chlorination of water as easy as possible, and because that leads many people to add chlorine every time they collect water, this is the cheapest way to prevent diarrhea among all the interventions for which there is evidence from randomized trials.
