In the light of the financial crisis of the US, it seems apparent that many economists are not scientists, they produce results that are consonant with an ideology and ignore inconvenient facts. In particular you may have seen the disputes between the salt-water and fresh-water economists in the US. "Is the intervention producing the intended benefits and what was the overall impact on the population? Could the program or project be better designed to achieve the intended outcomes? Are resources being spent efficiently?" Regarding measuring the performance of a program - it is a difficult problem. In a corporate environment, in my experience, people's behaviors change to optimize the metrics they are measured against, and that behavior may not be optimal or may even be detrimental for the organization as a whole. So let's assume there are no incentives to game the measurements. I suppose if you have a measurable objective - e.g., increase percentage of children who receive necessary vaccinations; or reduce incidence of some disease; or increase literacy rate, or increase rural electrification - then it is fairly straightforward to see whether you've reached your objective. A better designed program would reach the objective with less cost and effort. We tend to assume that things like I mention here improve the lives of people, but quantifying the benefit is hard. In particular, given limited resources, you may have to choose to do one of these several things - then which of the above things is the "best"? I'm not sure how you would figure that out.