A population pyramid is a bar chart showing the number of people in each age group, split by sex. The youngest are at the bottom, the oldest at the top; males on the left, females on the right. The shape of the pyramid reveals a country's demographic past, present, and future at a glance.

A true pyramid shape — wide base, narrow top — means high birth rates and high death rates. This is typical of pre-industrial societies and some sub-Saharan African countries today. The wide base shows many children; the narrow top shows few elderly. The population is young and growing fast.

A "beehive" or "domed" shape — narrower base, wider middle — means birth rates have fallen but the large youth cohorts are now working-age. This is the demographic dividend shape: countries like India and Mexico. The economy has a window of high productivity before the population ages.

A "skyscraper" or "column" shape — roughly equal bars from bottom to top — means low birth rates and low death rates. Most of Europe and North America look like this. The population is stable and aging slowly. Some countries, like Sweden, have maintained this shape through immigration.

An "inverted pyramid" — wider at the top than the bottom — means births are below replacement and the population is shrinking and aging. Japan, Italy, and South Korea show this shape. It signals a future of fewer workers, more retirees, and fiscal pressure. No country has reversed this shape once it set in.