“Measuring impact, particularly for research that involves people and is spread out over space and time, is never a straightforward matter. It is almost never as simple as collecting data before and after the intervention, since before-after estimates can be seriously biased by factors outside of the research. Even internally, selection biases and other confounding factors are often at play.”

Professor Paul J. Ferraro, economist at the Andrew Young School of Policy Studies at Georgia State University, said this while speaking on the issue of impact measurement at the World Agroforestry Centre (ICRAF) headquarters in Nairobi on 4 September. He emphasized, however, that despite the difficulties associated with impact measurement, it is the only way to tell for sure whether or not an intervention has done what we hoped it would. Read more. . .