World population outlook:Explosion or implosion?

Abstract

The world population was 7.7 billion in 2019, and the United Nations projects 9.7 billion in its medium-variant scenario, which assumes that world fertility continues to decline (from 2.5 children per woman in 2019 to 2.2 in 2050), and only 8.9 billion in its low-variant scenario in which fertility would decline even faster. Unless the entire world is hit by severe disasters on an unprecedented scale, it is difficult to imagine a world population much below 9 billion by 2050.