Many more impact evaluations could be done, and at lower unit cost, if evaluators could avoid the need for baseline data using objective socio-economic surveys and rely instead on retrospective subjective questions on how outcomes have changed, asked post-intervention. But would the results be...

Standard methods of impact evaluation often leave significant gaps between what we know about development effectiveness and what we want to know—gaps that stem from distortions in the market for knowledge. The author discusses how evaluations might better address these knowledge gaps and so be...