Data Source

A population pyramid traces the age structure of the global human population over a 150-year period, according to estimates and projections made by the United Nations. The controls at upper right allow forward and backward movement through time in steps of five years. Each bar in the pyramid represents the size of a five-year cohort—the number of males and females aged 0–4, 5–9, and so on. As time passes and people age, each cohort migrates upward through the pyramid. Meanwhile the bars shrink horizontally, reflecting age-specific death rates; the bottommost stratum is replenished by births. The data are from the United Nations Department of Economic and Social Affairs, World Population Prospects. The illustration was originally prepared with data from a 2010 report, which showed growth continuing past 2100. Revised numbers from the 2024 report reach a peak in the 2080s. At the end of the evolution, neither pyramid is very pyramidal: the 2010 graphic is bullet-shaped, and the 2024 one resembles an onion dome.

For more on the construction of the animated illustration, see “Computing Science: Pixels or Perish,“ American Scientist, Vol. 100, No. 2, March-April 2012, pages 106-111 (PDF).

Illustration created by Brian Hayes.