The structure and evolution of any population are determined by three fundamental variables:

: The incidence of death in a population. Improvements in healthcare and nutrition have led to a significant increase in global life expectancy, which rose by over eight years between 1995 and 2026.

Demography is the scientific study of human populations, primarily focusing on their size, composition, and spatial distribution, as well as the dynamic processes that drive change—, mortality , and migration . It is a multidisciplinary field, drawing on statistics, sociology, economics, and biology to analyze how individual life events shape global and local trends. The Core Pillars of Demography

: Birth rates begin to fall as society urbanizes and education (especially for women) increases.

: Both rates are low; the population stabilizes.