Estimates and projections: what the population numbers for past and future years mean
An estimate describes a year that has passed, built from censuses, surveys and registers. A projection describes a future year, calculated from assumptions about births, deaths and migration. In the UN data used here, estimates end in 2023 and projections start in 2024.
Estimates: the past, reconstructed
Even past population numbers are not simple counts. Censuses happen every ten years or so, not every country holds them on time, and every count misses some people. The UN Population Division combines censuses, surveys and civil registration into one consistent series for every country and year since 1950. Those numbers are estimates, and they are revised when new data arrive: each edition of the World Population Prospects can change the past a little.
Projections: the future, calculated
For years from 2024 on, the World Population Prospects 2024 contain projections. They start from the estimated population of each country by age and sex, and apply assumptions about future fertility, mortality and migration year by year.
A projection is not a forecast of what will happen. It shows what would happen if those assumptions held. The UN publishes several variants, for example with higher or lower fertility. Anthrotempo uses the medium variant, the one the UN presents as its main result.
For example, the UN projects a world population of 9.66 billion at mid-2050 and 10.2 billion at mid-2100, in the medium variant.
How the site labels them
- Every chart draws projected years with a dashed line and a shaded background.
- Tables mark projected rows, and texts say “projected” or “the UN projects”.
- Year pages for 2024 and later say “projected” in their heading.
Why it matters
The further a projection reaches, the more its result depends on its assumptions. Near-term projections of the people already alive are fairly solid, because those people exist and their numbers change mainly through deaths. Projections of births decades ahead depend on fertility assumptions that may not hold.
Last updated 26 October 2026