Population policies aim to modify the growth rate, composition, or distribution of a population. In practice, they can be explicit or implicit. The two main areas in which governments attempt to control or influence through population polices are fertility and migration. ‘Population policies and future challenges’ also considers some key population challenges of the 21st century. Will fertility rates fall to replacement in sub-Saharan Africa? What is the relationship between environment, population, and consumption in different parts of the world? How will we feed and provide water for the projected 9 or 10 billion of us by 2050? What will be the impact of the ageing of the world’s population and of technological change?