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Information about the Subnational Net Migration Estimates |
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Availability
| Valid From: .. | 03/01/1986 |
| To: .. | 06/30/2006 12:00:00 AM |
| Frequency: .. | Five-Yearly |
Design
Purpose: Estimates of the net migration component of population change between census years.
General Information ..
Contents
Introduction
Estimated Subnational Net Migration
Estimated Subnational Net Migration by Age and Sex
Published Estimates of Subnational Net Migration
Introduction
For a national population, net migration refers to external migration (movements between countries), and is the difference between external arrivals and external departures. For a subnational population, net migration includes both external migration and internal migration (movement within a country), and is the difference between external arrivals and external departures, plus the difference between internal arrivals and internal departures. However, it can be difficult to reliably measure these four sub-components of net migration.
Internal Migration
The five-yearly Census of Population and Dwellings provides some information on internal migration (eg via the question on 'address five years ago'). However, the census cannot collect information on people who have departed the country. There are also issues of non-response, undercount and residents who are temporarily overseas.
External Migration
External migration statistics are compiled from individual migration forms (arrival/departure cards) completed by all overseas travellers when arriving in and departing from New Zealand. The various classes of arrivals and departures are:
- short-term overseas visitors (involves a visit of less than 12 months)
- short-term NZ residents (involves a trip away of less than 12 months)
- permanent and long-term (PLT) migrants.
In the preparation of migration statistics the classification of passengers is primarily determined by individual passenger responses on the arrival and departure cards to the questions on intended length of stay/absence. If a person's intention changes later during the trip, then they may also change their migration category. For example, if a person comes to New Zealand with the declared intention of settling permanently, but in fact returns overseas after a few months, then that person is classified as a PLT migrant on arrival, but is later classified as a short-term visitor on departure. This is known as migration category jumping.
PLT arrivals include overseas migrants who arrive in New Zealand intending to stay for a period of 12 months or more (or permanently), plus New Zealand residents returning after an absence of 12 months or more. PLT departures include New Zealand residents departing for an intended period of 12 months or more (or permanently), plus overseas visitors departing from New Zealand after a stay of 12 months or more. The difference between arrivals and departures is known as net migration.
The arrival and departure cards ask travellers to give details of their full contact or residential address in New Zealand, and this information is coded to territorial authority (TA) area (city, district or territory). However, PLT migration data for territorial authority and regional council areas should be interpreted with caution, for the following reasons:
- It is possible that both arrivals and departures are overstated for the larger cities (especially those that are close to an international airport) and understated for the areas surrounding those cities.
- Some passengers provide a temporary address which does not reflect their usual residential address in New Zealand.
- Levels of non-response to the address question are higher for PLT arrivals than for PLT departures (possibly because many immigrants do not know their future residential address at the time of their arrival in New Zealand).
- Where regions straddle TA boundaries, the regional groupings used in this report consist of the territorial authority areas most closely associated with each region.
Estimated Subnational Net Migration
Because of the limitations of the data sources for external and internal migration at a subnational level, a 'residual' method can be used to estimate net migration. This method involves a rearrangement of the standard population equation:
Pop2 = Pop1 + Bths – Dths + Netmig
where:
Pop2 = population at end of period
Pop1 = population at start of period
Bths = births during the period
Dths = deaths during the period
Netmig = net migration for the period
- Note: The special case of ethnic populations, where there may be a component to allow for changing ethnic identity, is excluded from this discussion.
to:
Netmig = Pop2 – Pop1 – Bths + Dths
The estimated net migration is therefore calculated by subtracting estimated natural increase (births minus deaths) from the estimated population change between two dates.
Estimates of net migration using this method are available for regional council areas, territorial authority areas, main urban areas, North Island, South Island and New Zealand for each five-year period from 1981.
For 2001–2006, estimated population change is the estimated resident population at 30 June 2006 minus the estimated resident population at 30 June 2001; estimated natural increase is births (to mothers resident in each area) minus deaths (of people resident in each area) registered in the five years ending 30 June 2006.
For 1996–2001, estimated population change is the estimated resident population at 30 June 2001 minus the estimated resident population at 30 June 1996; estimated natural increase is births (to mothers resident in each area) minus deaths (of people resident in each area) registered in the five years ending 30 June 2001.
For 1991–1996, estimated population change is the census usually resident population count at 5 March 1996 minus the census usually resident population count at 5 March 1991; estimated natural increase is births (to mothers resident in each area) minus deaths (of people resident in each area) registered in the five years ending 31 March 1996.
For 1986–1991, estimated population change is the census usually resident population count at 5 March 1991 minus the census usually resident population count at 4 March 1986; estimated natural increase is births (to mothers resident in each area) minus deaths (of people resident in each area) registered in the five years ending 31 March 1991.
For 1981–1986, estimated population change is the census usually resident population count at 4 March 1986 minus the census usually resident population count at 24 March 1981; estimated natural increase is births (to mothers resident in each area) minus deaths (of people resident in each area) registered in the five years ending 31 March 1986.
Estimated Subnational Net Migration by Age and Sex
Estimates of subnational net migration by five-year age group and sex are derived by birth cohort. Net migration is calculated as a residual after applying live births (by sex) and deaths (by single-year of age and sex) for each year. For example:
Net migration between 1996 and 2001 for population aged 0–4 in 2001
- = Population aged 0–4 in 2001
– Births in five years ending 2001
+ 0.8 Deaths aged 0 in year ending 1997
+ Deaths aged 0 in year ending 1998 + ½ Deaths aged 1 in year ending 1998
+ Deaths aged 0–1 in year ending 1999 + ½ Deaths aged 2 in year ending 1999
+ Deaths aged 0–2 in year ending 2000 + ½ Deaths aged 3 in year ending 2000
+ Deaths aged 0–3 in year ending 2001 + ½ Deaths aged 4 in year ending 2001.
Net migration between 1996 and 2001 for population aged 5–9 in 2001
- = Population aged 5–9 in 2001
– Population aged 0–4 in 1996
+ 0.2 Deaths aged 0 in year ending 1997 + Deaths aged 1–4 in year ending 1997 + ½ Deaths aged 5 in year ending 1997
+ ½ Deaths aged 1 in year ending 1998 + Deaths aged 2–5 in year ending 1998 + ½ Deaths aged 6 in year ending 1998
+ ½ Deaths aged 2 in year ending 1999 + Deaths aged 3–6 in year ending 1999 + ½ Deaths aged 7 in year ending 1999
+ ½ Deaths aged 3 in year ending 2000 + Deaths aged 4–7 in year ending 2000 + ½ Deaths aged 8 in year ending 2000
+ ½ Deaths aged 4 in year ending 2001 + Deaths aged 5–8 in year ending 2001 + ½ Deaths aged 9 in year ending 2001.
Net migration for other five-year age groups from 10–14 to 80–84 years use a similar formula to that used for the 5–9 age group.
Net migration between 1996 and 2001 for population aged 85+ in 2001
- = Population aged 85+ in 2001
– Population aged 80+ in 1996
+ ½ Deaths aged 80 in year ending 1997 + Deaths aged 81+ in year ending 1997
+ ½ Deaths aged 81 in year ending 1998 + Deaths aged 82+ in year ending 1998
+ ½ Deaths aged 82 in year ending 1999 + Deaths aged 83+ in year ending 1999
+ ½ Deaths aged 83 in year ending 2000 + Deaths aged 84+ in year ending 2000
+ ½ Deaths aged 84 in year ending 2001 + Deaths aged 85+ in year ending 2001.
Published Estimates of Subnational Net Migration
Estimates of net migration are available on INFOS (Information Network for Official Statistics) for the periods 1982–1986, 1987–1991 and 1992–1996 using the respective census usually resident population counts for 1981, 1986, 1991 and 1996. Estimates of net migration are available for 1997–2001 and 2002–2006 using the estimated resident populations for 1996, 2001 and 2006.
Estimates of net migration for the periods 1982–1986, 1987–1991, 1992–1996, 1997–2001 and 2002–2006, and estimates of subnational net migration by age for 1997–2001 and 2002–2006, are available on the Statistics New Zealand website for all 16 regional council and 73 territorial authority areas:
http://www.stats.govt.nz/products-and-services/Articles/local-population-trends.htm
Output Variables
Output variables are pieces of individual information that can be extracted from the survey/output data. Often output variables can be cross tabulated with other output variables, for example sales by industry classification. The list below contains all current and past output variables which have been released for this survey/output.
Estimated Net Migration
Estimated Net Migration by Age and Sex
Changes in Output Variables over time
Guide to Interpreting Data
Summary of Changes to Survey/Output ..
| 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. |
| 1991 | Classification of urban areas revised into a three-part classification consisting of main, secondary and minor urban areas differentiated by population size. |
| 1 July 1992 | The number of regions increased to 16 following boundary reorganisation in the northern South Island. |
| 1996 | First post-enumeration survey held in New Zealand following the 1996 Census of Population and Dwellings. |
| 1996 | 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. Differences between mean estimates show little or no seasonal variation. 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.) The reference date for subnational population estimates and projections shifted from 31 March to 30 June. |
| 1999 | A revision of the age by sex estimates of the resident population was carried out in September 1999. The revision affected the age by sex estimates from 1991 onwards. The estimated totals for males, females and the total population remain unchanged. The revision was necessary because of data quality issues relating to the enumerated population at younger ages. Censuses in all countries tend to under-enumerate the population at all ages, and, in particular, the number of young children. Under-enumeration in the 1996 Census was confirmed by the first Post-enumeration Survey (PES) undertaken in New Zealand, which was carried out shortly after the 1996 Census. When post-censal estimates of the resident population were first produced following the 1996 Census, statistical adjustments were included for the estimated under-enumeration in the 1996 Census and for the estimated number of NZ residents temporarily overseas at census. The size of the PES limited the precision of the statistical adjustments for census undercount that were made. The precision of the adjustment for census undercount is particularly important for ages 0-5 years as for these ages estimates based only on births, deaths and external migration can provide alternative estimates to estimates built on census data. A demographic approach (ie using births, deaths and net permanent and long-term migration) has been used to provide a set of estimates for younger ages. |
| 1 Jan 2001 | Chatham Islands District became Chatham Islands Territory. |
| 2001 | Second Post-enumeration Survey carried out in New Zealand following the 2001 Census of Population and Dwellings. |
| 2002 | A revision of the estimated resident population of New Zealand 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. Population estimates for the period 1996-2001 use both the revised 1996-base population and the 2001-base population. They incorporate the intercensal discrepancy of 14,000 between 1996-based population estimates taken forward to 2001, and the new base population at 2001. Intercensal discrepancy is the difference between two population estimates that arises from errors in the census-based estimates and/or components of change. The intercensal discrepancy for 1996-2001 is introduced smoothly into the 1996-2001 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 dates of the 1996 and 2001 Censuses. |
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| 2004 | North and South Island series were updated using the following definitions:
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| 2006 | In March, Banks Peninsula District amalgamated with Christchurch City. All series refer to boundaries at 30 June 2006. |
Usage and Limitations of the Data ..The accuracy of net migration estimates using the 'residual' method is dependent on the accuracy of the population data (estimates or census counts), and the accuracy of the birth and death registrations.
Related Data Sources ..Census of Population and Dwellings
Population Estimates
Births
Deaths
External Migration
Sampling Errors ..
Non-sampling errors
Caveats on Release ..
Catalogue & Reference Numbers
| INFOS: | DNMC.S - Subnational net migration estimates (1986–1996) DNMC.S01 - Subnational net migration estimates (2001-2006) |
Other Comments
Classifications | Classification Versions | Classification Type |
TA04 - Territorial Authority 2004 | V2.0 | NZ Standard |
REGC04 - Regional Council 2004 | V1.0 | NZ Standard |
UA04 - Urban Area 2004 | V1.0 | NZ Standard |
Glossary of Terms
| Term | Description |
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| Census Usually Resident Population Count | A count of all people who usually live in a given area, and are present in New Zealand, on a given census night. The census usually resident population count of New Zealand excludes visitors from overseas and excludes New Zealand residents who are temporarily overseas. For a subnational area the count excludes visitors from overseas and elsewhere in New Zealand (people who do not usually live in that area), but includes residents of that area who are temporarily elsewhere in New Zealand on census night (people who usually live in that area but are absent). Residents are counted at the meshblock (smallest geographic area for statistical purposes) of their usual address. If insufficient information about a person's usual address is given, then the geographic information that is available is used to select (impute) a meshblock within that area. For example:
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| Estimated resident population | An estimate of all people who usually live in a given area at a given date. The estimated resident population of New Zealand includes all residents present in New Zealand and counted by the census (census usually resident population count), residents who are temporarily overseas (who are not included in the census), and an adjustment for residents missed or counted more than once by the census (net census undercount). Visitors from overseas are excluded. For a subnational area the estimate excludes visitors from overseas and elsewhere in New Zealand (people who do not usually live in that area), but includes residents of that area who are temporarily elsewhere on census night (people who usually live in that area but are absent). The estimated resident population at a given date after census is calculated by updating the base population for births, deaths and net migration (arrivals less departures) of residents of that area during the period between census night and the given date. National population estimates are produced quarterly (reference dates at 31 March, 30 June, 30 September and 31 December) and subnational population estimates are produced annually (reference date at 30 June). |
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| External Migration | The short-term and long-term movement of overseas and New Zealand travellers into and out of New Zealand. External migration statistics are compiled from individual migration forms filled in by passengers arriving in and departing from New Zealand, and forwarded to Statistics New Zealand by the Customs Department. The various classes of arrival and departure are: i. overseas visitors ii. New Zealand resident departing temporarily or returning after a short-term absence iii. permanent and long-term arrival iv. permanent and long-term departure. In the preparation of migration statistics the classification of passengers is primarily determined by individual passenger responses on the arrival and departure cards to the questions on intended or actual length of stay/absence. If a person's intention changes later, they may also change their migrant category (eg a person may come to New Zealand with the declared intention of settling permanently, but return overseas after a few months). Data users should recognise the limitations inherent in the information supplied by travellers. Statistics New Zealand introduced a systematic sampling method for the processing of short-term migration statistics in 1975. A random sample of all short-term migration declarations is processed each month. Consequently, all statistics relating to short-term migration are subject to sampling errors. However, from September 1997 total counts of short-term arrivals and departures of overseas visitors and New Zealand residents are actual counts which are not subject to sampling errors. Because all declarations for long-term migrants are coded, the possibility of sampling errors for this category of passenger does not arise. |
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| Internal Migration | The movement of people within the boundaries of a nation or region. |
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| Net Migration | The difference between arrivals and departures. |
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| Regional Councils (Regions) | The Local Government Commission established regional councils in 1989. Regional councils cover every territorial authority in New Zealand with the exception of the Chatham Islands District. The geographical boundaries of regions conform as far as possible to one or more water catchments. In determining regions, consideration was also given to regional communities of interest, natural resource management, land use planning, and environmental matters. |
| Resident population concept | A statistical basis for a population in terms of those who self-identify that they usually live in a given area at a given time. The census usually resident population count is a census measure of the resident population concept, and the estimated resident population is a demographic measure of the resident population concept. |
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| Subnational | Geographical units of a country (eg area units, territorial authorities, regional councils, urban areas) whose boundaries are defined for administrative, legal or statistical purposes. |
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| Territorial Authority | Territorial authority boundaries are defined by aggregations of area units. When defining the boundaries of territorial authorities, the Local Government Commission placed considerable weight on the ‘community of interest’. While the size of the community was a factor, the relevance of the components of the community to each other and the capacity of the unit to service the community in an efficient manner, were the factors on which the Commission placed most emphasis. |
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| Urban Areas | Comprises a three-part classification consisting of main, secondary and minor urban areas which constitute the ‘urban’ population of New Zealand. Main and secondary urban areas are centred on a major city or borough and include neighbouring boroughs, town districts and parts of counties which are regarded as suburban and belonging to that centre of population. |
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Contact Details
| Customer Service E-mail Contact: | info@stats.govt.nz |
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| Survey Enquiries E-mail Contact: | demography@stats.govt.nz |
Liability
Statistics New Zealand gives no warranty that the information or data supplied contains no errors. However, all care and diligence has been used in processing, analysing and extracting the information. Statistics New Zealand shall not be liable for any loss or damage suffered by the customer consequent upon the use directly, or indirectly, of the information supplied in this product.