The United Nations Statistics Division is the primary agency responsible at the international level for collecting official national statistics related to population size and density. These have been collected and disseminated on an annual basis through the Demographic Yearbook system since 1948.
More specifically, the following information are gathered:
- age and sex
- geographic areas (urban/rural, major geographic areas, cities with 100 000 population)
- marital status
- ethnocultural characteristics (i.e., national or ethnic origin, religion and language)
- size and type of nuclear family
- size and type of household
Other agencies or organizations that deal with population size and structure include
- United Nations Population Division prepares United Nations estimates and projections of population by age and sex for countries and areas of the world. These estimates and projections are based on national data provided by the United Nations Statistics Division. The latest estimates and projections of population size are published in the World Population Prospects. The Division also uses data on population density and urbanization as input for estimating urbanization. Those estimates are presented in World Urbanization Prospects.
- United Nations Human Settlements Programme (UN-HABITAT) looks at urbanization from a different angle. It collects, collates, analyses and reports data on national, urban/rural and city level in order to monitor human settlement conditions and trends.
- United Nations Permanent Forum on Indigenous Issues, in collaboration with the United Nations Statistics Division, review national practices of collecting and disseminating data on national and/or ethnic group, language and religion with special focus on indigenous persons.