Позитивные изменения. Том 2, № 2 (2022). Positive changes. Volume 2, Issue 2 (2022)

Insert 3: RANDOMIZED ASSIGNMENT OF SPRING WATER PROTECTION TO IMPROVE HEALTH IN KENIA

The link between water quality and health impacts in developing countries has been well documented. However, the health value of improving infrastructure around water sources is less evident.

Kremer et al (2011) measured the effects of a program providing spring protection technology to improve water quality in Kenya, with random assignment of springs to receive the treatment.

Approximately 43 percent of households in rural Western Kenya obtain drinking water from natural springs. Spring protection technology seals off the source of a water spring to reduce contamination.

Starting in 2005, the NGO International Child Support (ICS) implemented a spring protection program in two districts in western Kenya. Because of financial and administrative constraints, ICS decided to phase in the program over four years. This allowed evaluators to use springs that had not received the treatment yet as the comparison group.

From the 200 eligible springs, 100 were randomly selected to receive the treatment in the first two years. The study found that spring protection reduced fecal water contamination by 66 percent and child diarrhea among users of the springs by 25 %.

Source: Kremer, Michael, Jessica Leino, Edward Miguel, and Alix Peterson Zwane. "Spring Cleaning: Rural Water Impacts, Valuation, and Property Rights Institutions." Quarterly Journal of Economics 126: 145–205. 2011

WHEN CAN RANDOMIZED ASSIGNMENT BE USED?

Randomized assignment can be used in one of the two scenarios as follows:

1. When the eligible population is greater than the number of program spaces available. When the demand for a program exceeds the supply, a lottery can be used to select the treatment group within the eligible population. The group that wins the «lottery» is the treatment group, and the rest of the population that is not offered the program becomes the comparison group. As long as a constraint exists that prevents scaling the program up to the entire population, the comparison groups can be maintained to measure the short-term, intermediate, and long-term impacts of the program.

2. When a program needs to be gradually phased in until it covers the entire eligible population. When a program is phased in, randomization of the order in which participants receive the program gives each eligible unit the same chance of receiving treatment in the first phase or in a later phase of the program. Until the last group joins the program, it serves as a valid comparison group from which the counterfactual for the groups that have already been phased in can be estimated. This setup also allows evaluating the effects of differential exposure to treatment: that is, the effect of receiving the program for a longer or shorter time.

STEPS IN RANDOMIZED ASSIGNMENT

Step 1 — Define the units eligible for the program. Remember that depending on the particular program, a unit could be a person, a health center, a school, a business, or even an entire village or municipality.

Step 2 — Select a sample of units from the population to be included in the evaluation sample.

This second step is done mainly to limit data collection costs. If it is found that data from existing monitoring systems can be used for the evaluation, and that those systems cover the full population of eligible units, then a separate evaluation sample may not be needed.