Demographic Shifts: Aging & the Population Pyramid

From a booming young population to a shrinking, aging one, a country's age structure is shaped year by year by just two levers: how many children are born and how long people live. This simulation runs a real single-year cohort model — births feed the base of the pyramid, survival curves carry each age group forward, and the shape that emerges tells the whole demographic-transition story, from Nigeria's broad youth base to Japan's inverted, top-heavy pyramid. Adjust fertility and life expectancy, or jump straight to a preset, and watch decades of demographic change unfold in real time.