Rapid population growth is a phase in a demographic transition

When mortality falls before fertility does, populations grow rapidly: many more children survive while births remain high. As family size later declines, the growth rate slows, even while the total population may continue rising.

This article visualizes that transition across centuries and distinguishes historical estimates from future projections. Its chart has been updated with later UN data, so the projection is not a measurement of a future already determined.

The mechanism explains how a world can add many people while its percentage growth rate declines. It also leaves room for large differences between countries, whose age structures and fertility trajectories vary. Slower growth does not eliminate the challenge of providing good living conditions sustainably; it changes the shape and timing of that challenge.