Economists used to think wealth came from a combination of man-made resources (roads, factories, telephone systems), human resources (hard work and education), and technological resources (technical know-how, or simply high-tech machinery). Obviously, poor countries grew into rich countries by investing money in physical resources and by improving human and technological resources with education and technology transfer programs. Nothing is wrong with this picture as far as it goes. Education, factories, infrastructure, and technical know-how are indeed abundant in rich countries and lacking in poor ones. But the picture is incomplete, a puzzle with the most important piece missing.