Impact evaluation

An impact evaluation assesses the changes that can be attributed to a certain project, program or policy. In other words, the impact evaluation looks at what would have happened to those who benefitted from the project if in fact, they hadn't. Since it is impossible to have the same person both receive and not receive an intervention, the main challenge of every impact evaluation consists in building a plausible counterfactual (a group, similar to the treatment group both on observable and unobservable characteristics, but who didn't receive the treatment). A strong counterfactual allows one to identify causality between the intervention and observed outcomes.