Some may dispute the effectiveness of aid. But few would disagree that aid delivered to the right source and in the right way can help poor and fragile countries develop. It can be a catalyst, but not a driver of development. Aid now operates in an arena with new players, such as middle-income countries, private philanthropists, and the business community; new challenges presented by fragile states, capacity development, and climate change; and new approaches, including transparency, scaling up, and South-South cooperation. The next High Level Forum on Aid Effectiveness must determine how...