Population Structure, Pyramids, Dependency and Ageing Populations

Population structure refers to the composition of a population, most importantly its breakdown by age and sex. Structure matters enormously because a country with millions of children faces very different challenges from one with millions of retirees, even if both have the same total population. Geographers visualize structure using population pyramids and summarize dependency using ratios.

Population pyramids

A population pyramid is a pair of back-to-back horizontal bar charts. Age groups (usually in five-year cohorts) run up the vertical axis, males are shown on the left and females on the right, and the length of each bar shows the number or percentage of people in that group. Reading a pyramid is a core geographic skill: the base shows the youngest cohorts and the apex the oldest, so a