Data Sources

A description of the empirical data used and the methods applied in revising past estimates of population and components of demographic change (fertility, child, adult and overall mortality, international migration) is available here for each country or area for the period 1950 to 2023. For the countries with less than 1,000 inhabitants in 2023, only the data sources for total population are made available.

Select below a country or area to see the respective information, or download the whole set of metadata in PDF format for all countries or areas or a tabular version for each demographic component under Documentation.

New Zealand

Population: Total population and distribution by age and sex estimated to be consistent with the population by age and sex of the (a) 1951, 1956, 1961, 1966, 1971, 1976, 1981, 1986, 1991, 1996, 2001, 2006, 2013, 2018 censuses; (b) adjusted for under/over count; (c) official estimates through 2022; (d) only total population for 1945 Census; (e) International estimates used up to 2019; and with estimates of the subsequent trends in fertility, mortality and international migration.

Fertility: Total fertility rate and age pattern of fertility based on: (a) official estimates of age-specific fertility rates through 2018; (b) registered births classified by age of mother and the underlying female population by age through 2022; (c) adjusted for underregistration; (d) International estimates used up to 2019.  In addition, the (a) births in the household in the preceding 12 (or 24) months classified by age of mother from the 2006 Census; (b) indirect estimates obtained from the application of the reverse survival method to the 1951, 1956, 1961, 1966, 1971, 1976, 1981, 1986, 1991, 1996, 2001, 2006, 2013, 2018 censuses and 1958-2011 Education Stats; (c) cohort-completed fertility backdated by the mean age of childbearing from the 1976, 1981, 1996 censuses have been considered.

Child Mortality: Under-five mortality based on: (a) official estimates of infant and child mortality through 2018; (b) registered infant and child deaths through 2022.

Migration: International migration based on: (a) official figures of net international migration flows, and assumed subsequent trends in international migration; (b) estimates of migrant flows, and assumed subsequent trends in international migration; (c) information on foreign-born populations from censuses and registers from major countries of destination; (d) estimates derived as the differences between overall population growth and natural increase; (e) UNHCR statistics on the number of refugees in the main countries of asylum.

Disclaimer: This web site contains data tables, figures, maps, analyses and technical notes from the current revision of the World Population Prospects. These documents do not imply the expression of any opinion whatsoever on the part of the Secretariat of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.