Dimensionner l'aide au développement: ce que nous enseigne l'évaluation. Dimensioning Development Aid: Some Lessons from Evaluation

Most discussions on the development effectiveness of aid tend to focus on aggregate flows and neglect the various categories of aid and different aid delivery mechanisms. We emphasise, however, that the key question is not whether aid works, but which aid works. The potential effects – both beneficial and adverse – of aid appear to be mainly the consequence of how aid is provided. This paper therefore addresses two questions: which aid works and how aid is delivered. These issues are becoming increasingly relevant given the declining societal trust in public aid and against the background of the growing interests in the new aid architecture. We discuss three basic, albeit usually underestimated aspects that critically influence development effectiveness: (a) resource complementarities between different programme components, (b) substitution effects between different activities, and (c) spillover effects that influence aid effectiveness at aggregate level. We present some empirical examples of these mechanisms and indicate their particular relevance for the new types of institutional arrangements that characterise upcoming reforms of the international aid architecture (public-private partnerships, multi-donor trust funds and civil society support funds).