This GSDRC Topic Guide was written by Mareike Schomerus and Sherine El Taraboulsi-McCarthy (both of the Overseas Development Institute) with Jassi Sandhar. Its production was supported by the UK Government. GSDRC appreciates the contributions of Shivit Bakrania, James Golshetti, Rami Khouri, Dina Mansour-Ille, Aoife McCullough, Brian Lucas, Catherine Mueller, Jamie Pett,Lisa Stampnitzky, Craig Valters and Rebecca Wolfe. GSDRC Topic Guides aim to provide a clear, concise and objective report on findings from rigorous research on critical areas of development policy. Rather than provide policy guidance or recommendations, their purpose is to signpost policymakers and practitioners to the key debates and evidence on the topic of focus, to support informed decision-making.