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Explanatory Notes

Statistics New Zealand sources

Census of Population and Dwellings

A census of population and dwellings is conducted every five years under the authority of section 23(1) of the Statistics Act 1975. Statistics in this publication relate to the 2001 Census of Population and Dwellings, held on 6 March 2001.

The census normally occurs on the first Tuesday in March, a date that avoids school holidays and other events which mean significant numbers of people are away from home. It is also the time of year when fewer New Zealanders are overseas and provides the best opportunity to gain a true count of the population of New Zealand.

The census figures presented in “New Zealand: An Urban/Rural Profile” are based on the census usually resident population count. This refers to people who usually live in a given area and are present in New Zealand on census night. The count excludes visitors from overseas, and residents who are temporarily or permanently overseas on census night. For a subnational area, the count also excludes visitors from 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 who are away from their usual address on census night are allocated to the area where they usually live, and form part of the census usually resident population count for that area. For example, if a person usually lives in Christchurch but was in Wellington on census night, they will be included in the census usually resident population count for Christchurch.

Census counts give a snapshot of the population and are not adjusted for net census undercount and residents who are temporarily overseas. All census counts are randomly rounded to base 3.

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Population estimates

The estimated resident population of a given area is an estimate of all people who usually live in that area at a given date. It includes all residents of that area 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 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).

The estimated resident population of an area at a given date after census includes an update for births, deaths and net migration of residents for the period between census date and the given date. Subnational population estimates are produced annually (reference date at 30 June).


Population projections

The base population for the population projections is the estimated resident population of each area at 30 June 2001. These estimates are based on the 2001 census usually resident population count updated for:

  • net census undercount
  • residents temporarily overseas on census night
  • births, deaths and net migration between census night (6 March 2001) and 30 June 2001
  • reconciliation with demographic estimates at ages 0–9 years.

Projection assumptions are formulated after analysis of short-term and long-term historical trends, recent trends shown in other countries, government policy, information provided by local planners and any other relevant information.

The cohort component method is used to derive the population projections. In this method, the population for a given future date is calculated by updating the size of each age-sex cohort in the base population, for births, deaths and migration within each age-sex cohort according to the specified fertility, mortality and migration assumptions.

Although the assumptions made about future fertility, mortality and migration patterns of the population are carefully formulated to represent future trends, they are subject to uncertainty. Therefore, the projections should be used as guidelines rather than exact forecasts. They indicate the overall trend but do not attempt to project specific annual variation.

The projections do not take into account non-demographic factors (eg war, catastrophes) which may invalidate the projections. Demographic trends are monitored regularly, and when necessary projections will be revised to reflect new trends and to maintain their relevance and usefulness.


Vital statistics

Births and deaths data are now based on the resident population concept, replacing the de facto population concept used before 1991. While the de facto population concept refers to all vital events (births and deaths) registered in New Zealand, resident population concept excludes the births to, or deaths of, people who normally live overseas.

Live births exclude late registrations under Section 14 of the Births and Deaths Registration Act 1995. Section 14 births are births which were not registered in the ordinary way, that is when the birth occurred. Such registrations can occur as late as retirement age.


Household crowding

Household crowding is a theoretical concept about the acceptable number of people per household. Crowding generally refers to people's psychological response to density, that is, to their feelings of being crowded, having a lack of privacy or an increase in unwanted interactions or psychological distress. Crowding in households relates to situations where the number of people residing in a household exceeds the ability of the dwelling to provide adequate shelter and services to its members. In this report a household is deemed crowded if the dwelling the household resides in requires one or more bedrooms, according to the Canadian National Occupancy Standard.

The Canadian National Occupancy Standard (CNOS) sets the bedroom requirements of a household according to the following composition criteria:

  • there should be no more than two people per bedroom
  • parents or couples share a bedroom
  • children under five years, either of same or opposite sex, may reasonably share a bedroom
  • children under 18 years of the same sex may reasonably share a bedroom
  • a child aged five to 17 years should not share a bedroom with one under five of the opposite sex
  • single adults 18 years and over and any unpaired children require a separate bedroom.


Regional household expenditure estimates

Regional household expenditure estimates for 2001 are model-based and integrate data from the Household Expenditure Survey (HES) for the year ended 30 June 2001 with 2001 Census data.

Estimates of spending on various goods and services are modelled using household characteristics and expenditure information collected in the HES. These models are then applied to census data to produce regional estimates of household expenditure.

The household expenditure and average household expenditure estimates are for the year ended 30 June 2001. Data for average household expenditure is based on counts for occupied permanent private dwellings, excluding visitor only households, from the 2001 Census. Household expenditure for the apparel group is not available for New Zealand or South Island areas.

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New Zealand income survey

The New Zealand Income Survey (NZIS) is run annually during the June quarter as a supplement to the Household Labour Force Survey (HLFS). Data is collected from all respondents to the HLFS, and only from proxies if people were unable to answer on health or language grounds.

Average weekly income relates to the respondent’s most recent pay period. The data collected are cash only, pre-tax (gross) income and do not include any non-cash fringe benefits. Interest and investment income has only been collected since 2002. Average weekly income may therefore not represent total income.

The HLFS sample comprises approximately 15,000 private households, sampled on a statistically representative basis from rural and urban areas throughout New Zealand. The final NZIS dataset consists of approximately 24,000 valid person records, and 4,000 imputed person records.

Two types of error are possible in estimates based on a sample survey: sampling error and non-sampling error. Sampling error is a measure of the variability that occurs by chance because a sample, rather than an entire population, is surveyed. Sampling errors are available on request.

Non-sampling errors include errors arising from biases in the patterns of response and non-response, inaccuracies in reporting by respondents, and errors in the recording and coding of data. Non-sampling errors are not quantified.

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New Zealand business demography statistics

The number of full-time equivalent persons engaged (FTEs), and number of business locations, are derived from the Statistics New Zealand Business Frame, a database of New Zealand businesses and their structure. It records details such as name, location, predominant type of industrial activity performed, employment levels, and the degree of overseas ownership.

The Annual Business Frame Update Survey (AFUS) is conducted in mid-February each year to update the records on the Business Frame. All full-time equivalent data are rounded. Percentages are calculated from rounded figures.

Businesses are identified from the Goods and Services Tax (GST) registrations supplied by Inland Revenue. For businesses providing financial services and deemed to be providing 'exempt supplies' under the Goods and Services Tax Act 1985, the sources used are:

  • association lists
  • financial reports
  • list of superannuation/pension schemes from the Government Actuary.

FTEs are derived as the total number of full-time employees and working proprietors plus half the number of part-time employees and working proprietors. Employees and working proprietors working 30 hours or more per week are defined as full-time. Those working less than 30 hours per week are defined as part-time.

Each separate operating unit engaged in one, or predominantly one, kind of economic activity from a single physical location or base is known as a business location (or geographic unit). An enterprise is a business or service entity operating in New Zealand. It can be a company, partnership, trust, estate, incorporated society, producer board, local or central government organisation, voluntary organisation or self-employed individual.

The population for the Business Demographic Statistics includes only businesses that are economically significant.

A business is said to be economically significant if it meets one or more of the following criteria:

  • greater than $30,000 annual GST expenses or sales
  • more than two full-time equivalent paid employees
  • in a GST exempt industry (except for residential property leasing and rental)
  • part of a group of enterprises
  • registered for GST and involved in agriculture or forestry.

All GST registered enterprises recorded on the Inland Revenue client registration file are continually monitored to determine if they meet the 'economic significance' requirements for 'birth' onto the Business Frame. A buffer zone of $25,000 to $35,000 exists to prevent enterprises switching excessively between 'economically significant' and 'economically insignificant'. For example, an economically significant enterprise whose annual GST turnover drops to $27,000 would not be reclassified as economically insignificant, but one whose annual GST turnover drops to $23,000 would be reclassified. All non-trading and dormant companies are excluded from these statistics.

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Building consents

Data on building authorisations is obtained each month from all territorial authorities. GST is included in the figures collected.

Under the building regulations, effective from 1 January 1993, building authorisations are applied for under the building consents system administered by territorial authorities. Prior to this date, applications were made under the building permits system. The building consents system, however, has wider coverage than the building permits system. The additional coverage includes some government building (particularly work on education buildings), and on-site drainage and reticulation work.

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Other government sources

Land Transport Safety Authority, 1997/98 Travel Survey

The Land Transport Safety Authority interviewed approximately 14,000 people from 7,000 randomly sampled households. Respondents were interviewed at home between June 1997 and July 1998, and during April and May 1999. People were asked to describe all their travel, by car, motorcycle and other motor vehicles, by train or plane, by bicycle, and on foot, for two consecutive days (called travel days). As these days were spread over a year, information could be scaled up to represent a year's travel by all New Zealanders.

Respondents were asked to record each part of any trip they undertook on those days, even a simple walk to a nearby shop. For example, someone going to work might drive from home to a parking building and then walk to their workplace. Each part of the trip (one by car, one on foot) was recorded in detail. The distance of the driving trip was computer-calculated by locating the point of origin, the point of destination, and by measuring the road distance between the two.

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Ministry of Health, 2001 Social Deprivation Index

The Social Deprivation Index is a measure of socio-economic status calculated for small geographic areas. The calculation uses a range of variables from the 2001 Census of Population and Dwellings which represent nine dimensions of social deprivation. The Social Deprivation Index is calculated at meshblock level, and built up to the relevant geographic scale using weighted average census usually resident population counts. The nine variables (proportions in small areas) in decreasing weight in the index are:

1 Income People aged 18–59 receiving a means tests benefit
2 Employment People aged 18–59 years who are unemployed
3 Income People living in equivalised1 households with income below an income threshold
4 Communication People with no access to a telephone
5 Transport People with no access to a car
6 Support People aged less than 60 years living in a single parent family
7 Qualifications People aged 18–59 years without any qualifications
8 Living Space People living in equivalised1 households below a bedroom occupancy threshold
9 Owned Home People not living in own home

(1) Equivalisation: method used to standardise household composition and size.

The Social Deprivation Index is provided in two forms, a continuous score and an ordinal scale.

The first principle component score is the result of the calculation using the nine weighted census variables. The scores are scaled to have a mean 1000 index points and standard deviation 100 index points.

The decile rating is derived from the first principle component score. The ordinal scale ranges from 1 to 10, where 1 represents the areas with the least deprived scores and 10 the areas with the most deprived scores.

Note that the deprivation index applies to areas rather than individuals who live in those areas.

More information 


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