After two decades working in development, Claire Melamed is ready to reveal a dirty secret about her work. Many of the numbers that lie behind life-and-death decisions in developing countries are, as she puts it, “a bit shaky”. If you don’t know how many people live somewhere and who’s dying when of what, you can’t make well-informed decisions to help them. Now she and others are working to change that by getting better data and using it smarter. Listen to what that means in practice and the story of Justice Aheto, whose award-winning mathematical models could also be life-saving for malnourished children in his native Ghana.