At its core, economic development in poor countries relies on moving workers out of agriculture and into more productive activities. But even people who live in cities need to eat, so agricultural productivity must increase. Drawing on a lifetime of experience in developing countries, Timmer clearly describes the vital role that agricultural transformation plays in structural economic change, the risks involved, and the pitfalls to avoid. The process of shifting away from agriculture has happened in countries all over the world, sometimes smoothly, sometimes not. Governments have helped the process but have also hindered it, often in the name of food security: to reduce hunger in rural areas, officials have subsidized farmers or protected them against imports, even though doing so often impedes development and prolongs poverty. Timmer worries that a rush to shift the focus of agriculture from growing food to producing biofuels might prevent the doubling of food production that must occur over the next four decades to meet the needs of growing populations and changing diets.