The 20th Century growth of global democracy fostered a history-making economic boom for many. But stagnant wages and growing inequality over the last few decades have frustrated millions and inspired nationalist and protectionist political movements. In her new book, “Edge of Chaos: Why Democracy Is Failing to Deliver Economic Growth – and How to Fix It” (Basic Books), economist Dambisa Moyo explores what it will take to preserve both representative government and economic opportunity.