What these actors have in common is a firm belief in measuring success (i.e. return on investment) through quantifiable indicators. These developments have multiplied the demand for rigorous impact evaluation, meta-analysis and evidence mapping.

A call for a comprehensive approach

Yet, despite a long history of interdisciplinary work and many interesting recent developments, the evaluation profession has not sufficiently lived up to the challenge of presenting a comprehensive approach. We therefore call for a more systematic integration of methods with a view to bringing together quantitative measures of results achieved and a thorough understanding of the underlying causal mechanisms. In other words, evaluations must get out of the trenches where either answering the question of “how much” was achieved or “why” and “how” is the predominant focus. Indeed, by building on encouraging theoretical developments and making better use of new types of data, it will be possible to answer both questions in a rigorous fashion.