When world trade is costly, a country can profitably industrialize only if its domestic markets are large enough. In such a country, for increasing returns technologies to break even, sales must be high enough to cover fixed setup costs. We suggest two conditions conducive to industrialization. First, a leading sector, such as agriculture or exports, must grow and provide the source of autonomous demand for manufactures. Second, income generated by this leading sector must be broadly enough distributed that it materializes as demand for a broad range of domestic manufactures. These conditions have been important in several historical growth episodes.

A country's most talented people typically organize production by others, so they can spread their ability advantage over a larger scale. When they start firms, they innovate and foster growth, but when they become rent seekers, they only redistribute wealth and reduce growth. Occupational choice depends on returns to ability and to scale in each sector, on market size, and on compensation contracts. In most countries, rent seeking rewards talent more than entrepreneurship does, leading to stagnation. Our evidence shows that countries with a higher proportion of engineering college majors grow faster; whereas countries with a higher proportion of law concentrators grow slower.