Anthrotempo
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Photo: NASA Earth Observatory/NOAA NGDC

Methodology

Every number on Anthrotempo is calculated from published data by code that is the same for every page and tool. Nothing is typed in by hand. This page explains each method in plain words. The data sources, with their licences and file checksums, are listed on the data sources page.

Data

  • Population by single year of age, by sex, on 1 January of every year from 1950 to 2101, for 237 countries and areas, six regions and the world: UN World Population Prospects 2024, with the official update of January 2026.
  • Summary indicators (population on 1 July, births, deaths, median age, life expectancy at birth, fertility, net migration) from the same release.
  • Estimates run to 2023. From 2024 on, all figures are projections in the UN medium variant, and the site labels them as such (see the guide to estimates and projections).
  • Countries and areas are the UN’s, within their present borders for every year (see the country pages for the note on boundaries).

The data are checked before they are published: the ages must add up to the published totals, the sexes to both sexes, and the year files must hold the same numbers as the country files. Every file is recorded with its checksum.

Reference dates

Population figures are either for 1 January (everything about single ages) or for 1 July (the UN’s summary indicators). Births and deaths are totals over a calendar year. Each figure says which. For a date between two 1 Januaries, the population is interpolated in a straight line, age by age, and never extrapolated beyond the published years.

Birth cohorts

On 1 January of year Y, people aged a completed years were born between 2 January of Y − a − 1 and 1 January of Y − a. Anthrotempo calls that group “born in Y − a − 1”. The one-day shift moves about 0.3 % of a year’s births. Once a cohort reaches the oldest group, 100 and over, it can no longer be followed on its own.

Age percentile

The share of people younger than you is the sum of everyone younger than your completed age, plus part of the people of your exact age, divided by the total. Within one year of age, people are assumed to be spread evenly over the year: someone halfway to their next birthday counts half of their own age group as younger. In the open oldest group no such assumption is made, and the result is a range.

Median age and age groups

The median age shown in summaries is the UN’s own (1 July). Where Anthrotempo derives a median from the 1 January ages, it spreads people evenly within each year of age and says the value is derived. “Under 15” and “65 and over” are counts of single ages. Dependency ratios count people by age only, not who works.

Changes and comparisons

  • Absolute change is the later value minus the earlier one.
  • Relative change is only given from a valid, nonzero starting value.
  • Changes in percentages are given in percentage points.
  • Comparisons only use figures from the same data release, so editions are never mixed.

Generations

Generation names cover ranges of birth years from one cited definition (Pew Research Center). The site uses the names for those ranges only and never describes what a generation is like.

The 3D globe

In Humanity in 3D each dot stands for the same number of people. The dots are shared out among the countries by the largest-remainder method, so they add up exactly to the world total, and they stand in a column above each country’s label point, youngest at the bottom. The dots are symbols, not places where people live. The table under the globe has the same numbers.

In the Migration globe each arc joins two countries along a great circle. Its width is 1.5 pixels plus 9 pixels times the square root of its number of people divided by the largest connection shown, so the largest connections do not hide the smaller ones. Highlighting changes the colour, never the width. Nothing moves along an arc: the data are people living abroad at mid-year, not journeys.

In the City globe the area of a disc grows with the city’s population. From afar, the cities in each cell of the same width in kilometres are drawn as one ring at their population-weighted centre, with their total, so no one is left out at any zoom.

Development indicators and urbanisation

Internet use, access to electricity and adult literacy come from the World Bank’s World Development Indicators, the Human Development Index from UNDP’s Human Development Report, and the degree of urbanisation from the UN World Urbanization Prospects 2025.

  • Each value is shown with the year it was observed. A missing year is never filled in or interpolated, and a value from another year than the one asked for is labelled with its own year.
  • World Bank and UNDP data are matched to the UN countries and areas by ISO code. Regional and income aggregates are never mixed with countries.
  • The Human Development Index is recalculated for past years with every UNDP report, so only one release is used at a time.
  • The degree of urbanisation classes every 1 km² of land by one rule for all countries: cities have at least 50,000 people at 1,500 or more per km², towns and semi-dense areas at least 5,000 people at 300 or more per km², the rest is rural. Its years from 2026 on are UN projections.
  • Population figures always come from the World Population Prospects, never from the World Bank’s own population series, so populations from different editions are not mixed.

Life tables and longevity

  • Life expectancy and survival come from the UN complete period life tables of the World Population Prospects 2024: single ages 0 to 100, by sex, for every year from 1950 to 2100.
  • Life expectancy at an age is read from the table for that age. It is never calculated by subtracting an age from the life expectancy at birth.
  • The chance of living from one age to another is the ratio of survivors at the two ages in the same year’s table.
  • These are period measures that describe one year’s mortality, not forecasts for any person (see the guide to period and cohort life expectancy).

Ageing measures

  • Shares and ratios are calculated from the population by single age on 1 January, and each states what it is divided by: the whole population for a share, the people aged 15 to 64 for a dependency ratio (see the guide to dependency ratios).
  • A threshold such as 80 or more counts every age from the threshold up to the open group of 100 and over.
  • The year in which people aged 65 or more outnumber children under 15 is the first year from which this stays true in every later year of the series.

Population scenarios

  • The medium projection is the median of the UN probabilistic projections, and the bands are their 80 and 95 percent prediction intervals.
  • Variants are the UN’s deterministic projections, each changing one assumption. They are drawn as separate lines and never as a range of uncertainty (see the guide to variants and intervals).
  • Variant and interval series begin in 2024 and are joined to the estimate for 2023, so the lines meet.

International migrants

  • Migrant stocks at mid-year come from the UN International Migrant Stock 2024, for eight reference years from 1990 to 2024. No years in between are interpolated.
  • The people from a country living abroad are the UN’s own world total for that country of origin. A migrant share divides the stock by the population on 1 July of the same year from the World Population Prospects.
  • The basis of each country’s count (country of birth or citizenship, with or without refugees, UN estimate) is shown with it.
  • A stock is never presented as a yearly flow (see the guide to stocks and flows).

Cities

  • City populations come from the cities file of the UN World Urbanization Prospects 2025, drawn by the degree of urbanisation (see the guide to city definitions). Years in which a city had fewer than 50,000 people stay empty.
  • Cities with 1 million people or more in 2025 have their own page. Names are written as the UN publishes them.
  • Rankings within a country use the 2025 population. Growth since 2000 is the relative change from the 2000 value. Years from 2026 on are UN projections.

Generated texts

The sentences on country and year pages are chosen from the data: a sentence about a peak, a crossing or a rank appears only when the data show it. Numbers in sentences are rounded to three significant figures, the tables beside them give the exact values.

Privacy

Your birthday and other personal entries stay in your browser. Analytics receive only the birth year and the generation, if you have agreed to analytics. Details are in the privacy policy.

Last updated 26 October 2026