In America, almost all the money in circulation passes through financial institutions every day. But in Nigeria\'s \"cash and carry\" system, 90 percent of the currency never comes back to a bank after it\'s issued. What happens when two such radically different economies meet and mingle, as they have for centuries in Atlantic Africa? The answer is a rich diversity of economic practices responsive to both local and global circumstances. In Marginal Gains, Jane I. Guyer explores and explains these often bewildering practices, including trade with coastal capitalism and across indigenous currency zones, and within the modern popular economy. Drawing on a wide range of evidence, Guyer demonstrates that the region shares a coherent, if loosely knit, commercial culture. She shows how that culture actually works in daily practice, addressing both its differing scales of value and the many settings in which it operates, from crisis conditions to ordinary household budgets. The result is a landmark study that reveals not just how popular economic systems work in Africa, but possibly elsewhere in the Third World.