Population pyramid – three shapes and forecasting by birth and death rates

GeographyPopulation & SettlementAges 15–16

A population pyramid by 5-year age group (male on the left, female on the right) shows three shapes: expansive (wide base, young population, fast growth), stationary (even sides, slow growth) and constrictive (narrow base, aging population, decline). Drag the birth-rate and death-rate sliders, then press Run: population is forecast year by year with the cohort-component method (births enter the 0–4 group, deaths applied by age, survivors move up a group), and the pyramid gradually changes shape while total population, natural increase rate, the share of three age groups and the current pyramid type are shown.