Austen Davis1, Zoe Matthews2, Sylvia Szabo3, Helga Fogstad4. 1. Section for Global Health, Norwegian Agency For Development Cooperation, Oslo, Norway. 2. Department of Social Statistics and Demography, University of Southampton, Southampton SO17 1BJ, UK. Electronic address: z.matthews@soton.ac.uk. 3. Department of Social Statistics and Demography, University of Southampton, Southampton SO17 1BJ, UK. 4. Department of Global Health, Education and Research, Norwegian Agency For Development Cooperation, Oslo, Norway.