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Geography

Population change and structure

Population numbers change over time, influenced by births, deaths and migration into or out of the area. Global population levels, having grown slowly for most of human history, are now rising.

Global population growth

Population pyramids show the structure of a population by comparing relative numbers of people in different age groups. Population structures differ markedly between LEDCs [LEDC: A Less Economically Developed Country (LEDC) has low levels of development, based on economic indicators, such as gross domestic product (the country's income). ] and MEDCs [MEDC: A More Economically Developed Country (MEDC) has high levels of development based on economic indicators such as gross domestic product (the country's income). ].

Demographic transition models show population change over time - and also show marked differences between LEDCs and MEDCs.

At present the world's population is growing quickly, though this has not always been the case.

  • Until the 1800s the world's population grew slowly for thousands of years.
  • In 1820 the world's population reached one billion.
  • In the early 1970s, the world's population reached three billion.
  • In 1999, less than 30 years later, the population doubled to six billion.
  • The global rate of population growth is now one billion every 15 years.

The graph shows this pattern of accelerating growth (including the predicted population for 2025).

World population growth 500BC - 2025

World population growth 500BC - 2025

Back to Population index

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