This volume, the first in a new series on Population and Sustainable Development, provides new ways of thinking about population trends in the 21st century. While the 20th century was the century of population growth with the world's population increasing from 1.6 to 6.1 billion, this book shows that the 21st century is likely to see the end of world population growth and become the century of population ageing. At the moment we are at the crossroads of these two different demographic regimes, with some countries still experiencing high population growth while others are already faced with...