Separate reference year, release vintage, and access date
A population value's reference year describes when the estimate refers to. A release or estimate vintage identifies the data publication that supplied it. An access date records when a reader or site retrieved that publication. These dates answer different questions and should not be collapsed into one label.
The World Bank's Population, total metadata says values are midyear estimates and documents sources and limitations, including variation in national statistical concepts and methods. A value can be an estimate rather than a same-year headcount. Consult the World Bank indicator metadata and the individual series used for a particular place.
Why two inputs may not share one year
Population estimates are refreshed on their publisher's schedule; geographic area values may be attached to a different boundary vintage or series. The Census Bureau's population-estimates program publishes its own releases, while its GEOINFO products describe geographic attributes. Check the relevant Population Estimates Program information and Census land-area guidance rather than inferring a shared reference date from a page's publication date.
Area series can also have their own definitions. For example, the World Bank's land-area indicator has a stated scope that is not automatically interchangeable with a water-inclusive area measure. The source years are shown separately on Atlas Compare profiles; a density calculated from inputs with different dates is labelled as a calculation, not represented as a synchronized official statistic.
How to read a comparison with different dates
- Check the year attached to each population value, not just the page's update date.
- Check the area definition and boundary vintage separately.
- Treat calculated density as derived from the displayed inputs.
- Do not describe values as same-year or directly equivalent when their source periods differ.
The methodology page records the bundled source snapshot and known gaps. You can inspect individual country profiles and state profiles or see the displayed inputs side by side in a selected comparison.