An age‑sex pyramid visualises the structure of a population by stacking male and female cohorts for successive age intervals, typically five‑year bands. The horizontal axis represents the size of each cohort, while the vertical axis orders the cohorts from youngest at the base to oldest at the top.
Demographers use the pyramid to infer past events such as wars, migrations, or health crises, because abrupt bulges or deficits in specific age‑sex slices leave a distinctive imprint. A broad base suggests high fertility, whereas a constricted middle may signal elevated mortality or emigration.
Mathematically, the proportion of a given cohort is expressed as a ratio of its absolute count to the total population. This ratio can be converted to a percentage for easier visual comparison.
What is an age-sex pyramid?
How does the horizontal axis in an age-sex pyramid represent data?
What can demographers infer from a broad base in an age-sex pyramid?
How are abrupt bulges or deficits in specific age-sex slices significant?
What does the vertical axis of an age-sex pyramid represent?
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