Book excerpt: This book summarizes five years of learning from data collected as part of the Global Accelerator Learning Initiative. The authors present data describing impact-oriented ventures and accelerators that operate in both high-income countries and in emerging markets. Blending survey data with insights from sector experts, their various analyses shed light on the basic structure of accelerators, showing where they are having their most promising results. Unlike previous studies, this book does not focus on a few high-profile accelerators (like TechStars and Y Combinator) and startups (like AirBnB and Uber). Instead, it compares a range of accelerator programs that target specific impact areas, challenging regions, and marginalized entrepreneurs. Therefore, it serves as a valuable tool for scholars, policymakers, and practitioners interested in the effectiveness of accelerator programs as tools that unleash the economic potential currently trapped in entrepreneurial dead spaces.