Population
The total number of people living in a country or territory, counting all residents regardless of legal status or citizenship.
How it is measured
National statistical offices run periodic censuses, then produce annual mid-year estimates between census rounds using birth, death, and migration registers. International bodies harmonize these into comparable series.
Where the number came from
Counting people is one of the oldest functions of a state: Rome ran a census, and England produced the Domesday Book in 1086. But the modern national census is an Enlightenment invention, beginning with Sweden in 1749, the United States in 1790, and Britain in 1801, each built to apportion taxes or parliamentary seats rather than to satisfy curiosity. The idea that every country should publish a comparable total on a common schedule is much younger still: the UN Statistical Commission and Population Division, both created in the late 1940s, pushed the world onto decennial census rounds and shared definitions. That history is why the number behaves the way it does. A national population is not a measurement taken this year. It is the last census, rolled forward with registered births, deaths and migration, then harmonised after the fact so one country’s total can sit honestly beside another’s.
Worked example: why two careful sources disagree about India by 44 million
The Factbook’s final edition, frozen on 22 January 2026, put India at 1,419,316,933 and China at 1,407,181,209, both labelled 2025 estimates: a gap of about 12 million, near enough to call the two countries level. Our live World Bank series for the same reference year puts India at 1,463,865,525 and China at 1,406,585,000, a gap of about 57 million. China barely moved between the two sources. India moved by roughly 44.5 million, about the population of Spain. Neither source is wrong, and neither is out of date. India’s last full census was taken in 2011 and the next has been postponed repeatedly, so every current Indian figure is a projection stretched fifteen years past its anchor, and the two agencies stretched it on different assumptions about fertility decline and undercount. China, censused in 2020 with well-registered vital statistics, leaves far less room to disagree. When two credible sources give different populations for the same country and year, the size of the gap is usually telling you how old the last census was.
Figures read from our own population table; each row there carries its observation year and whether it came from a live feed or the frozen archive.
Our data source
World Bank World Development Indicators (SP.POP.TOTL), which draws on the UN Population Division and national offices. IMF WEO fills gaps such as Taiwan.
Refresh cadence: The World Bank refreshes WDI roughly quarterly; we take the latest observation on each rebuild.
What to watch for
Figures for the current year are always estimates, not counts. Conflict states and countries with old censuses (for example Lebanon or DR Congo) carry wide uncertainty bands. Sources can disagree by tens of millions for large countries depending on revision cycles.
CIA World Factbook equivalent field: "Population" (frozen at the January 2026 final edition; our figures continue from live sources).