American Scientist

We live at a unique time of transition in human history. Populations in some parts of the world are growing rapidly, while others are stabilizing or declining. At the same time, age distributions are shifting at different rates in different regions. The populations of Niger and the Democratic Republic of the Congo, for example, are still quite young, whereas Italy and Japan are much older. Even within countries, there are growing gaps in population growth rates and age structures across urban, suburban, and rural areas.