Productivity growth is the key driver of sustainable income growth and poverty reduction. Its effects on human welfare are enormous. While economists agree on the importance of productivity, its measurement and drivers remain elusive. We sometime refer to productivity as a "residual" or even as a "measure of our ignorance." This important book analyzes the trends and drivers of productivity growth, with a special focus on emerging and developing countries. It uses state-ofthe-art econometric techniques and brings together the analysis of a wide range of productivity drivers which, so far, have been analyzed in isolation. It also discusses the impact of COVID-19 on productivity growth. Reading this book will help in reducing our ignorance on the most important driver of human well-being.