Book excerpt: The 20th century was the century of explosive population growth, resulting in unprecedented impacts; in contrast, the 21st century is likely to see the end of world population growth and become the century of population aging. We are currently at the crossroads of these demographic regimes. This book presents fresh evidence about our demographic future and provides a new framework for understanding the underlying unity in this diversity. It is an invaluable resource for those concerned with the implications of population change in the 21st century. The End of World Population Growth in the 21st Century is the first volume in a new series on Population and Sustainable Development. The series provides fresh ways of thinking about population trends and impacts.