APPLICATION OF DIFFERENCE-IN-DIFFERENCE TECHNIQUES TO THE EVALUATION OF DROUGHT-TAINTED WATER CONSERVATION PROGRAMS

A nonexperimental evaluation's validity can be threatened by a number of factors that are well known in the program evaluation literature. T his article illustrates some of the internal validity threats that ari se when evaluating the impact of water conservation programs implement ed during a drought. These include differential response to the drough t because of imbalance in the control and participant group characteri stics, self-selection bias, and the impact of measurement error This a rticle shows how to deal with these problems in the context of water c onservation programs when high-qualify disaggregate data are available .