There are five billion people on Earth

What actually happened

The number depends entirely on when you were in school. World population hit 5 billion in 1987, 6 billion in 1999, 7 billion in 2011, and 8 billion in 2022. Whatever figure you memorized is wrong now, and it was probably wrong within a few years of your exam.

The more interesting change is the shape of the curve rather than the number on it. The exponential-growth framing that dominated classrooms from the 1970s onward, and the population-bomb literature behind it, described a real trend that has since bent. The global fertility rate fell from about 5 births per woman in 1960 to roughly 2.2 today, and much of the world is now below replacement. Population is still growing, driven by momentum and rising life expectancy, but the UN projects a peak this century followed by decline. The demographic anxiety in your textbook has largely inverted: a growing number of countries now worry about having too few people.