The milestone of 7 billion—projected to be reached on 31 October 2011 will be marked by achievements, setbacks and paradoxes. While women are on average having fewer children than they were in the 1960s, our numbers continue to rise. Globally, people are younger and older than ever before. In some of the poorest countries, high fertility rates hamper development and perpetuate poverty, while in some of the richest countries, low fertility rates and too few people entering the job market are raising concerns about prospects for sustained economic growth and the viability of social security systems.