However, there is no such perfect control group due to the geographical, economic and social specificities of each area. Empirical economists working on evaluations of such projects have found ways to deal, under certain hypotheses, with the “counterfactual problem”. Moving from the ideal evaluation via a randomised experiment (rarely able to be performed properly and usually costly), to evaluation techniques such as matching, regression discontinuity, instrumental variables and selection of observables relies on strong assumptions. The literature has come up with solutions that need to be carefully considered before applying them. A combination of country-level and project level monitoring helps to understand whether the overall level of action at the time of assessment is adequate. However, the combination of project and national-level evaluations is in practice extremely difficult.