Demography is the scientific and statistical study of human populations, focusing on their size, composition (such as age, sex, ethnicity), and how these populations change over time due to the interplay of three main processes: fertility (births), mortality (deaths), and migration (movement of people)

. Demographers analyze population dynamics to understand how populations grow, shrink, or transform, and they use this knowledge to make forecasts about future population size and structure. This is crucial for government planning, business strategies, and social policy development

. Demography also studies the distribution of populations geographically and socially, including factors like education, nationality, religion, and economic status

. While primarily focused on human populations, demography can extend to related fields such as biodemography, which looks at genetic and biological aspects of populations

. The discipline relies on data from censuses, surveys, and administrative records to measure population characteristics and changes, often producing vital statistics like birth rates, death rates, and migration flows

. In summary, demography is the quantitative description and analysis of populations, their structures, and the factors driving their changes over time