The Economist reports on Ben Ramalingam's new book, "Aid on the Edge of Chaos." "The most interesting part of Mr Ramalingam's book, "Aid on the Edge of Chaos", is his discussion of how some agencies are beginning to learn from the way poor people can successfully do difficult things - such as bringing up well-nourished children on meagre incomes-without external experts or programmes. Learning from such "positive deviants", but also experimenting repeatedly and quickly, has much to offer the world of aid."