Non-resident fellow Paul Romer argues that the principal constraint to raising living standards in this century will come neither from scarce resources nor limited technologies. Rather it will come from our limited capacity to discover and implement new rules—new ideas about how to structure interactions among people, such as land titles, patents, and social norms. The central task of reducing global poverty is to find ways for developing countries to adopt new rules that are known to work better than the ones they have. Economists who advise leaders on policy have often overlooked why some good rules get adopted and others do not. But a better understanding of rules-that-change-rules could lead to breakthrough thinking about development policy. The special rules of China’s Special Economic Zones, where new cities like Shenzhen could grow up, created small laboratories through which rules from Hong Kong spread to the mainland, helping unleash the largest and fastest reduction of poverty on record. Romer concludes that a new type of development policy would be to voluntarily charter new cities for the purpose of changing rules, using a range of new legal and political structures analogous to the ones that made Hong Kong and Shenzhen possible.