Even after the 1990s, when much of the world seemed to finally embrace market‐oriented policies, there is a lack of understanding about what makes nations grow. William Lewis spent a dozen years studying how firms in the formal and informal economy operate in countries around the world. He will explain why the key to improving economic conditions in poor countries is to increase competition. Removing internal barriers to growth will raise productivity, the factor that accounts for large differences in wealth, including wealth among rich countries. Simon Johnson will assess Lewis’s insights on the impact of regulation, taxes, and size of government on productivity in countries as diverse as Brazil, Germany, Russia, and the United States.