There has been an unprecedented political focus on economic development and poverty reductions since the Gleneagles Summit of 2005, yet it seems economists have been unable to agree on how to capitalise on the opportunity. Is more aid the solution? Or the problem? This article argues that, beyond the headline-grabbing generalities, development economists are building up a detailed body of empirical evidence specific to individual countries which will shape more effective policy interventions in the years ahead. As in many other areas of applied economics, there is a quiet revolution in what economists know and consequently in their policy advice.