Human Population Increase

 The long-term trajectory of global population growth, as analyzed by the Our World In Data group, illustrates a radical demographic shift characterized by a period of historic acceleration followed by a predicted slowdown.

Historically, population growth was exceptionally slow. The global population grew by only 0.04% annually between 10,000 BCE and 1700. The rapid population increase that defines the modern era did not begin until after 1800, leading the population to increase eightfold from approximately 1 billion to around 8 billion today.

A particularly interesting way to understand the speed of this change is by examining the time it took to add each subsequent billion people to the world's total:

Key Developments in Time to Add Each Billion

The data highlights that the period required to add one billion people shrank dramatically during the mid-20th century before beginning to expand again, signaling the slowdown in population growth.

• The First Billion: It took all of human history until approximately 1805 to reach the first billion inhabitants.
• The Early 20th Century: The time needed to add the next billions shrank significantly. It took 120 years (1805–1925) to reach two billion, and then only 35 years (1925–1960) to reach three billion.
• The Peak Acceleration: The fastest period of growth occurred from 1974 to 2011, during which the world added the 5th, 6th, and 7th billions. Each of these milestones required only 12 to 13 years to achieve.

The Slowdown Trend

The core development in recent decades is that the world has now surpassed this peak rate of growth. The global population growth rate peaked in 1962 and 1963 at an annual rate of 2.2% and has since halved. This reduction means that, in absolute terms, the world population is no longer growing exponentially, but rather, the time between added billions is lengthening.

Future projections by the UN underscore this deceleration:

• It is estimated to take approximately 14 years to reach nine billion (projected for 2037).
• It is then projected to take 21 years to reach 10 billion (projected for 2058).
• The latest UN medium projection anticipates that the world population will peak at 10.4 billion in 2086 before beginning to fall.

This shift toward slowing growth rates is explained by the demographic transition, a phenomenon where rapidly declining mortality rates are followed by declining fertility rates. Because fertility rates have dropped—driven by factors like female empowerment, increasing children's well-being, and wider access to contraception—low fertility, rather than high mortality, is expected to keep future population changes small.