National Population Estimates
National Population Estimates
Statistics New Zealand
Statistics New Zealand
To provide population data between census dates, Statistics New Zealand estimates the population, using the most recently available census data as a base.
The estimated resident population is updated regularly for population change due to births, deaths and net migration (arrivals less departures) of residents.
The national population estimates give the best measure of the population that usually lives in an area, for a limited range of variables (age and sex) for total New Zealand area.
The estimates apply either to the number of people at a particular time ('at') or the average over a period of time ('mean'), usually a year (or quarter).
Estimated national populations (total, or subgroups defined by age and sex) are used for many purposes in all areas of society and the economy; including planning, policy formation, making business decisions and monitoring change in health and education.
They are also widely used in analysing changes in the demographic, economic and social structure of New Zealand, eg in the calculation of mortality rates, participation rates in education, per capita consumption of goods within New Zealand, electoral enrolment rates, and crime rates, etc.
First Post-enumeration Survey held in New Zealand following the 1996 Census of Population and Dwellings.
The population concept used for population estimates and projections changed from de facto to resident.
The de facto population includes all persons in New Zealand at a given time. It includes overseas visitors, but excludes residents temporarily overseas and net census undercount.
The estimated resident population includes the estimated net census undercount and the estimated number of residents temporarily absent overseas, but does not include overseas visitors.
Resident population estimates do not show the quarterly fluctuations that de facto estimates are subject to because of seasonal changes in the numbers of overseas visitors temporarily in New Zealand, and changes in the numbers of New Zealand residents temporarily out of New Zealand.
A revision of the estimated resident populations for the period 1991–1996 was carried out in August 1997.
The revision was necessary because the 1996 Census and the 1996 Post-enumeration Survey (PES) allowed a new base population for population estimates to be defined at 30 June 1996.
Over the period 1991-95 revised mean year ended estimates of the de facto population were about 2% smaller than the corresponding estimates of the resident population. (The revised de facto estimates used information from the 1991 and 1996 Censuses while the resident estimates only used information from the 1996 Census.)
In September, a revision of the age by sex estimates of the resident population was carried out.
The revision affected the age by sex estimates from 1991 onwards.
The estimated totals for males, females and the total population remain unchanged.
In October, estimates for 1998 and 1999 already published were revised to correct for a shortfall in birth registrations during 1998 (as indicated by birth notifications received from hospitals).
Second Post-enumeration Survey carried out in New Zealand following the 2001 Census of Population and Dwellings.
A revision of the estimated resident populations for the period 1991-2001 was carried out in September 2002.
The revision was necessary for two reasons. Firstly, the 2001 Census and the 2001 Post-enumeration Survey (PES) allowed a new base population for population estimates to be defined at 30 June 2001. Secondly, a revision of population estimates based on the 1996 Census was necessary, as analysis of the 2001 PES results led to revised estimates of undercoverage in the 1996 Census, from 1.2% to 1.6% in total.
About 16,000 residents were added to the 1996-base population because of the revised undercoverage estimates.
Population estimates for the period 1991-1996 use the revised 1996-base population.
Third Post-enumeration Survey carried out in New Zealand following the 2006 Census of Population and Dwellings.
A revision of the estimated resident populations for the period 2002–2006 was carried out in August 2007.
The revision was necessary because the 2006 Census and the 2006 Post-enumeration Survey (PES) allowed a new base population for population estimates to be defined at 30 June 2006.
A revision of the estimated resident population for the period 2007–2013 was carried out in August 2014.
The revision was necessary because the 2013 Census and the 2013 Post-enumeration Survey (PES) allowed a new base population for population estimates to be defined at 30 June 2013.
A revision of the estimated resident population for the period 2013–2019 was carried out in August 2019.
The revision was to incorporate the outcomes based migration measure, to transition from the intentions-based measure after passenger departure cards were discontinued in November 2018.
The intentions based measure classified migrants according to the intended length of stay or absence they stated at the time of their border crossing, whereas The outcomes-based migration measure links traveller histories over time and classifies travellers as migrants according to where they started, and whether they spend more than 12 of the next 16 months in, or out, of New Zealand following the border crossing.
The intentions-based measure over-stated gains from net migration compared to the outcomes-based measure, resulting in a provisional downwards revision for the March 2019 quarter.
Additionally, due to the 16-month lag before estimates of migration flows can be finalised, population estimates will be provisional for 18 months, to allow for quarterly revision.
A revision of the estimated resident population for the period 2013–2020 was carried out in September 2020 to fully incorporate the 2018 Census and 2018 Post-enumeration survey. Due to the outcomes-based migration component, population estimates will be provisional for 18 months, to allow for quarterly revision.
Estimated resident populations (by age and sex) aid the decisions of government, business and community organisations.
They are also widely used in analysing changes in the demographic, economic and social structure of New Zealand, eg in the calculation of mortality rates, participation rates in education, per capita consumption of goods within New Zealand, etc.
For the calculation of rates when the numerators or "top lines" relate to data covering calendar years, mean year ended 31 December population estimates are appropriate as denominators or "bottom lines".
For analysing data collected over a short time period (eg a month), estimates of the population at the end of the closest quarter are appropriate as the denominator or "bottom line".
The accuracy of population estimates depends on the accuracy of the population base and on the accuracy of the components (births, deaths and migration) used to update population estimates. Some users of population estimates are more interested in accurately monitoring population change rather than in monitoring the overall accuracy of population estimates. Here the accuracy of the base population is discussed separately from issues of accuracy in the components of population change.
The base estimated resident population is derived by adjusting the census population for net census undercount as enumerated by the Post-enumeration Survey (PES) and estimates of residents temporarily overseas at census date (based on external migration and census data).
The uncertainty in the net undercount estimated from the 1996 PES had a survey error (twice the standard error) of 7,000. Thus, at 95% confidence, because of uncertainty in the PES alone, the resident population of New Zealand at 5/3/96 could be up to 7,000 higher or lower than the estimated resident population at 5/3/96. The uncertainty in the net undercount estimated from the 2001 PES had a survey error of 10,000; for the 2006 PES the survey error was 8,000.
Residents temporarily overseas (RTOs) at census are estimated using the length of absence data from the migration arrival and departure cards. At the 1996 Census an estimated 40,000 (survey error 1,100) New Zealanders were temporarily overseas ie just over 1% of the NZ resident population. Migration data is the only comprehensive source of data on RTOs; only 16,700 or 42 percent of RTOs were captured by the 1996 Census as absentees overseas (note that whole households may be away overseas at census). At the 2001 Census an estimated 54,500 New Zealanders were temporarily overseas. At the 2006 Census an estimated 63,900 New Zealanders were temporarily overseas. This estimate was based on matching migration arrival and departure records; it is not possible to assign a measure of accuracy to these estimates.
After the most recent census, national population estimates are updated quarterly using registrations of births and deaths, and permanent and long-term migration, captured by the migration cards. It is necessary to estimate the number of births and deaths that occurred during the most recent quarter as not all of the births and deaths that occurred in the current quarter will be registered by the end of the quarter.
Births and deaths that occurred in the most recent quarter are estimated from registered births and registered deaths, with estimation errors (twice the standard error) of 520 for provisional estimated births and 240 for estimated provisional deaths. Estimation errors for final estimated births and final estimated deaths are smaller, about 200 for births and 0 for deaths (but with a slight negative bias of about 8 deaths missed per quarter). With births and deaths running about 60,000 and 30,000 respectively per year (since the 2006 census up from 55,000 and 27,000 respectively after 2001 census) the final annual estimation error for births amounts to about 400 or 0.7%, while for deaths the annual negative bias of 32 is only about 0.1% of annual deaths (one part in a thousand).
Registrations of births data and deaths data in New Zealand can be regarded as complete. Virtually no births or deaths escape the registration process for any length of time. A highly conservative estimate might be that records are 99.5 percent complete. This would equate to approximately 280 births and 140 deaths being missed on average each year. However we have no evidence of any such under-reporting.
Defining migrant status by the outcomes-based method measures changes in their resident status based on their actual length of stay in New Zealand over a 16 month period following their travel. Classification of migrant status by the outcomes-based method observes travellers’ past classification history by the 12/16 rule, as well as their travel sequences over a 16-month follow up period. The migration estimates will be provisional for 18 months, to allow for quarterly revision.
Population estimates for the period 1991-1996 are based on the 1996 Census; note that as no Post-enumeration Survey was held after the 1991 Census it is not possible to derive a base resident population for 1991.
Revised estimates of the resident population for 1996-2001 incorporate the intercensal discrepancy between 1996-base population estimates taken forward to 2001, and the new base population at 2001.
Revised estimates of the resident population for 2002–2006 incorporate the intercensal discrepancy between 2001-base population estimates taken forward to 2006, and the new base population at 2006.
Revised estimates of the resident population for 2007–2013 incorporate the intercensal discrepancy between 2006-base population estimates taken forward to 2013, and the new base population at 2013.
Revised estimates of the resident population for 2013–2018 incorporate the intercensal discrepancy between 2013-base population estimates taken forward to 2018, and the new base population at 2018
Intercensal discrepancy is the difference between two population estimates that arises from errors in the census-base estimates and/or components of change. The intercensal discrepancy is introduced smoothly into the revised population estimates, with the size of the adjustment for the intercensal discrepancy depending on the relative closeness of the date of the estimate to the beginning and end of the intercensal period.
See Data collections - Methodology, for further information.
- Statistics New Zealand
- Ministry of Education
- Ministry of Health
- Government Planners/Local Body Planners
National Population Estimates – information releases
Historical population estimates tables
Maori population estimates
Coping with the discontinuity in population estimates in 1991
Effects of changing from de facto population estimates to resident population estimates
Principles and protocols for producers of Tier 1 statistics