Sources & method
Every figure on this site comes from open, official data. Where a number depends on how a place is defined, we say which definition we used.
Why the same place can have several correct populations: how many people live in London.
Annual population series
Year-by-year figures on our trends pages are official mid-year population estimates: from the Office for National Statistics for England and Wales, National Records of Scotland for Scotland, and NISRA for Northern Ireland, retrieved via the ONS Nomis service. They are published under the Open Government Licence v3 and cover every local authority from 2001 onwards. New estimates are published each year, and these pages are updated when they land.
Country totals
National populations come from the UN World Population Prospects 2024, medium variant, which is the standard source for international comparison and states its vintage. It covers 233 of the 246 countries and territories we list; the remainder are places the UN reports under a parent state (Hong Kong and Macao under China, Åland under Finland) or that are not UN members, and those keep a GeoNames figure which is labelled as such on the page.
WPP also supplies the series from 1950 and the projections to 2050 shown on country pages. Figures beyond the current year are projections, not measurements, and are marked.
Current population of towns
Current town and city populations come from GeoNames, released under the Creative Commons Attribution 4.0 licence. GeoNames figures are for the populated place, which for large cities is close to the urban core rather than the wider local-authority or metropolitan area.
Why lists disagree
A city, its urban area and its council can be three different populations. London is about 8.9 million as a continuous urban area, but the City of London alone holds a few thousand residents. When lists disagree, this is usually why. We label the definition rather than pick one and hide the choice.
Corrections
If a figure looks wrong, it may be a definition mismatch or a stale source record. We would rather fix it than defend it.