Subnational Population Estimates

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Abstract

Population estimates are produced for geographical units of New Zealand (eg area units, territorial authorities, regional councils) whose boundaries are defined for administrative, legal or statistical purposes.

The estimation of subnational populations uses the same component methodology as for estimates of the national population, but with the addition of an extra component – internal migration between the subnational areas of New Zealand.

External migration for each territorial authority (ie movements between the TA and outside New Zealand) is estimated from external migration data. Internal migration is estimated since there is no direct source of annual internal migration data.

The estimated resident populations for these subnational areas at 30 June are produced annually. They are constrained to agree with the corresponding national estimated resident population.

Purpose

Subnational population estimates are used in many administrative, statistical and research applications.

They are used by Government, regional planning authorities, local bodies, private organisation, researchers and individuals for determining future housing and other consumer needs, community amenities and social services at the subnational level.

Subnational estimates of population also provide information on the supply of labour for employment and the growth of markets.

Citation Information

Title

Subnational Population Estimates

SubTitle

Regional Council Population Estimates Territoral Authority Population Estimates Area Unit Population Estimates Urban Area Population Estimates Local Govenment Area Population Estimates

Alternate Title

SPE

Creator

Statistics New Zealand: Population Statistics

Publisher

Statistics New Zealand

Rights

Statistics New Zealand

Series Information

Series Name

Subnational Population Estimates

Description

Population estimates give the best available measure of the size and age-sex structure of the population usually living in an area. Estimates are based on the latest census data and on births, deaths, and migration since the census.

Coverage Information

Temporal Coverage

  • 1996 to present

Topical Coverage

  • Births
  • Deaths
  • International migration
  • Internal migration
  • Population
  • Subnational
  • Regional Council
  • Territoral Authority
  • Area Unit
  • Urban Area

Publication

Significant events impacting this study series

1988:

Local Government Amendment Act No 3 provides for the constitution of 14 Regional Councils.

The regional council areas cover every territorial authority area in New Zealand with the exception of Chatham Islands County.

These replaced 22 Local Government Regions.

1 Nov 1989:

Local government reorganisation creates 74 Territorial Authority areas. These replaced 213 Local Authorities.

1 July 1992:

The number of regions increased to 16 following boundary reorganisation in the northern South Island.

1 Jan 2001:

Chatham Islands District became Chatham Islands Territory.

1 March 2004:

Tauranga District became Tauranga City.

March 2006:

Banks Peninsula District amalgamated with Christchurch City.

December 2008:

Statistics New Zealand adopted a new method for producing subnational population estimates by age group and sex.

This new method was used to revise subnational population estimates, at 30 June 2007 but did not affect the total population estimate at each subnational area.

1 Nov 2010:

A new unitary authority (the Auckland Council) became operational. Two districts (Rodney and Papakura) and four cities (North Shore, Waitakere, Auckland and Manukau) became part of the new Auckland Council area.

The Franklin District was divided between three territorial authority areas: Auckland, Hauraki District, and Waikato District.

2011:

Following the 2010/11 Canterbury earthquakes a number of additional data sources were used to assess subnational population change during the June 2011 year.

These data sources are described in Estimating local populations after the 2010/11 Canterbury earthquakes. (http://www.stats.govt.nz/browse_for_stats/population/estimates_and_projections/estimating-pop-after-chch-quakes-paper.aspx)

2011:

The regional council and territorial authority areas for the subnational population estimates at 30 June 1996 forward were rebased on boundaries at 1 July 2011.

2012:

Alternative data sources have been further utilised for subnational (regional councils, territorial authorities, and area unit) population estimates.

Primary Health Organisation enrolment data, electoral enrolments, and IR tax data.

Net migration at the 15–24 ages is partly determined by historical patterns. Some differences compared to the historical population estimates trends will occur in terms of geographic areas, by age groups and sex. However, these differences are minimal and should have low or no impact on our data users.

Usage and limitations of the data

Usage

Subnational population estimates are used in many administrative, statistical and research applications.

They are used by Government, regional planning authorities, local bodies, private organisations and individuals for determining future housing and other consumer needs, community amenities and social services at the subnational level. Subnational estimates of population also provide information on the supply of labour for employment and the growth of markets. Subnational estimates are available at 30 June; these estimates can be used as a proxy for mean year ended 31 December population estimates.

Limitations of subnational estimates

Population estimates give the best available measure of the size and age-sex composition of the population usually living in an area. However, uncertainty is inherent in the estimation process.

Statistics New Zealand produces subnational population estimates using a component methodology, where estimates of the components of population change (births, deaths, and migration) are used to update a base population.

Subnational population estimates are constrained to the national estimates and, therefore, the quality of subnational estimates is affected by the quality of the components of national estimates. There are also some additional uncertainties that arise when estimating the components of population change at the subnational level, particularly estimating net migration (external/international and internal migration combined) for subnational areas. Due to these factors, uncertainty generally increases with reference dates further from the base (starting-point). Uncertainty also increases as population estimates are broken down by age, sex, and geographic area.

It is important to note that population estimates for small geographic areas (eg area units) are more uncertain than estimates released at broader geographic levels because information on external and internal migration is often not readily available at the area unit level and localised developments (eg greenfield subdivisions) can have a significant impact on the net migration patterns and population structure of area units, but this impact can be difficult to identify.

Due to regional differentials in census undercount, and the propensity of residents to be temporarily overseas at census, it is difficult to quantify the accuracy of subnational estimates. An evaluation of subnational population estimates produced during the 2002–06 period identified that, five years out from the 2001 base population, relative errors were less than 5 percent for 60 out of 73 territorial authority areas. For the ten territorial authority areas with a population greater than 100,000, relative errors ranged from an underestimate of -2.2 percent (Manukau City) to an overestimate of 0.5 percent (Auckland City).

It is not possible to ascertain the accuracy of current post-censal estimates as no independent authoritative measure of the resident population exists. Since 2006, Statistics NZ has implemented a number of changes to its estimation methods aimed at improving the accuracy of population estimates. This has included the use of new data sources and refined methods for using existing data sources.

The periodic Census of Population and Dwellings remains the cornerstone of population statistics in New Zealand. Following the 2013 Census it will be possible to derive updated estimates of the population, to assess the accuracy of estimates since 2006, and to revise estimates where necessary.

Data accuracy

We cannot ascertain the accuracy of current population estimates as no independent authoritative measure of the resident population exists. Since 2006, we have implemented a number of changes to our estimation methods, aimed at improving the accuracy of population estimates. This included using new data sources and refining methods for using existing data sources.

See data collections - methodology for further information.

Main users of the data

Statistics New Zealand, Ministry of Education, Ministry of Health, Government Planners/Local Body Planners, researchers

Frequency

4 Annual

Revision Information

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DDI Id
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DDI Version
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