Demography

Demography is the statistical study of populations, especially human populations. It examines size, structure, distribution, and how these attributes change over time due to births, deaths, and migration. Demographic analysis describes past trends, explains their determinants, and projects future population dynamics. Key indicators include population size and density, age and sex structure, birth rate, total fertility rate, mortality rate, life expectancy, and net migration. Related concepts include aging, urbanization, dependency ratios, and sex ratios.

Data sources and methods: Demography relies on censuses, vital statistics (births and deaths), population registers, and surveys. Analytical methods include life tables, age- and sex-specific rates, birth and death rate calculations, cohort analysis, and the cohort-component method for projections. Geographic and longitudinal data support subnational analyses and trend comparison.

Subfields: fertility and family demography; mortality and health demography; migration and mobility; population aging; urbanization; and population projections and scenario analysis. Applications: informs public policy in health care, education, housing, labor markets, pension systems, and environmental planning.

History: The discipline traces to early quantitative work by John Graunt in the 17th century and was advanced by Thomas Malthus and later 20th-century demographers. The development of systematic data collection—censuses, vital statistics, and international data programs—solidified demography as a formal field within the social sciences and policy planning.