Glossary
A plain-language dictionary for population history.
From basic demography to how we handle uncertain data, every term used on this site is defined here — written for readers with no background in statistics.
TFR, growth rates, age structure, and the core concepts behind population science.
How we measure, estimate, and project population — and where uncertainty comes from.
The three open datasets we stitch together — HYDE, Gapminder, and UN WPP — and what each covers.
What each visual element on the chart means — source band, cursor, ridgelines, and more.
B
Whether population is shown by today's borders or by the countries that existed at the time.
C
The steady yearly growth rate that would take a population from its start value to its end value.
A copyright license that lets anyone reuse data, as long as the original source is credited.
Population figures pieced together from historical records and censuses, roughly 1800 to 1949.
D
The number of children and older people compared with the number of working-age people.
How many years it takes a population to double in size at its current growth rate.
G
An open dataset of long-run country statistics, used here for population figures from 1800 to 1949.
H
A historical reconstruction of population back to 10,000 BCE, built from archaeology and land-use models.
L
The average number of years a newborn would live if death rates stayed the same as today.
M
The age that splits a population exactly in half: younger on one side, older on the other.
N
Births minus deaths in a population, not counting people moving in or out.
The number of people entering a country minus the number leaving, over a given period.
O
Each country's ridgeline is sized to its own highest point, not a shared scale across countries.
P
A country card you keep on screen so you can compare it against whatever else you're viewing.
A chart of how many people are in each age group, split by sex, stacked from youngest to oldest.
The UN's central estimate of future population, one of several scenarios it publishes.
R
A population estimate for a time before written records, built from indirect evidence.
A new release of a dataset that replaces earlier figures with updated methods or information.
One country's population history, drawn as a single hill-shaped band on the canvas.
S
The year where one source dataset ends and the next begins; methodology may differ on either side.
The coloured strip above the chart that shows which dataset covers each era.
T
How years are spaced on the horizontal axis — linear, weighted, or logarithmic.
The average number of children a woman would have over her lifetime, if current birth rates held steady.
U
A population figure from the UN World Population Prospects, based on census and survey data.
The 2024 edition of the UN World Population Prospects — the main source for data from 1950 onward.