Development cooperation has spent decades wrangling over the merits, evidence, and implications of what we may term "the learning hypothesis": the idea that increased knowledge by development organisations must logically lead to increased effectiveness in the performance of their development...

Over the last two decades, national development agencies have committed to results-based approaches and to putting evidence at the centre of their decision-making. For evidence “optimists”, this is a much-needed corrective to past practice; in contrast, “pessimists” worry about ideology...