World population reached 8 billion in 2022. It took hundreds of thousands of years to reach 1 billion, and only two centuries to add the next 7 billion. Population growth is an increase in the number of people in a population. It is calculated as births minus deaths plus net migration.

Growth rates are uneven. Sub-Saharan Africa is growing fast. Europe and East Asia are shrinking or stagnating. The global rate peaked in the late 1960s and has been falling since. But the absolute number of people continues to rise because of population momentum — large numbers of young people entering reproductive age.

Drivers and consequences

• High fertility rates
• Declining mortality, especially child mortality
• Immigration
• Strain on food, water, housing, and jobs
• Aging populations in low-growth regions

Thomas Malthus predicted catastrophe. He was wrong about timing, but the question of limits remains. Whether growth is a problem depends on consumption, technology, and distribution. A small population with high consumption can stress the planet more than a large population with low consumption.