Demography (from Ancient Greek __ δῆμος (_dêmos) 'people, society' and
__ -γραφία (-graphía)_ 'writing, drawing, description') is the statistical
study of human populations: their size, composition (e.g., ethnic group, age),
and how they change through the interplay of fertility (births), mortality
(deaths), and migration.
Demographic analysis examines and measures the dimensions and dynamics of
populations; it can cover whole societies or groups defined by criteria such
as education, nationality, religion, and ethnicity. Educational institutions
usually treat demography as a field of sociology, though there are a number of
independent demography departments.