The contribution of entrepreneurial businesses to economic growth is a frequently debated topic among the academic and policy-making communities and the subject of much discussion in the business and popular press. This debate stems from the enormous heterogeneity across entrepreneurs. A small share of entrepreneurs exhibit high growth and contribute substantially to job creation, innovation and productivity growth. However, the vast majority either fails or doesn’t grow. For both measurement and conceptual reasons, this heterogeneity is not well understood. Understanding this heterogeneity requires tracking the career paths of entrepreneurs including the differences in socio-economic circumstances across entrepreneurs. It also requires studying the obstacles and challenges facing entrepreneurs such as the difficulties of starting up businesses and obtaining financing. To complicate matters further entrepreneurs operate in a constantly changing economic and technological environment. This volume explores these issues from a number of different perspectives. A common theme is the need for improved economics measurement of entrepreneurial activity. Chapters in this volume take stock of our existing knowledge and data infrastructure on measuring entrepreneurial activity and offer insights and perspective on how to make improvements in the future. The chapters fit into three broad themes but with substantial overlap especially given the focus on economics measurement. The first broad theme is to explore entrepreneurial heterogeneity. The second broad theme is the challenges that entrepreneurs face and how this has varied over time including over the business cycle. The third broad theme focuses on core data and measurement issues and gaps.