The most comprehensive count of the New Zealand population is derived from the Census of Population and Dwellings, conducted by Statistics New Zealand (Tatauranga Aotearoa) every 5 years. It is an official count of all people and dwellings New Zealand on Census night, and collects details of age, sex and other characteristics of New Zealand's population. The Statistics Act 1975 prescribes that a census be conducted every 5 years and provides a basic outline of Census content, though questions can and do change over time. The last New Zealand Census was conducted on 7 March 2006. The 2011 Census was not held on 8 March 2011 as planned, due to the Christchurch earthquake on 22 February 2011. The Census was held on 5 March 2013.
Census statistics are used as the basis for estimating the population at national and regional levels, for electoral purposes and the distribution of government funds. They are used by individuals and organisations in the public and private sectors for planning, administration, research and decision making.
Populations are estimated in various ways. It is important to understand how a population has been derived when you are using the data.
Census data in the Community Profile section of profile.id® is predominantly based on usual residence data, while some household and dwelling information is based on place of enumeration. The estimated resident population can be found in the Additional Information section of this website.
Usual residence population
This population is derived from the Census. It is the place where a person usually lives, rather than the place where they were counted on Census night. Each person completing the Census is required to state their address of usual residence and this information is used to derive the Usual Residence population at the meshblock level.
Usual Residence is the main method of assessing the population in the Census, and information on this basis is available back to 1996. Because of this it is used as the default option in profile.id®, and all data relating to individuals is presented based on their usual residence.
This population counts people where they are on Census night, regardless of whether it is their usual address or not. Enumerated population is not used for most of the profile topics, however topics concerning households and dwellings have to use a form of enumerated data, as households which are away from their usual address on Census night don’t have their household characteristics recorded at their place of usual residence.
The information presented in the tables in the Community Profile is based on detailed tables produced by Statistics New Zealand. Statistics NZ take confidentiality of data very seriously, and there are five basic rules in place to ensure that information is only used in aggregate, and no data about individuals can be ascertained from the Census data.
The geographic areas used in profile.id® have been designed to accommodate these rules. For instance, each area must have a minimum population of 543 persons at every Census year (1996, 2001 and 2006). This is the minimum population size required to have no data cells confidentialised under “Rule 3: Mean Cell Size”, based on the classifications which are part of the profile.
All cells in a Census table are randomly rounded to base 3. This means that random adjustments are made to all cells in the table so that each number is a multiple of 3.
Table totals and subtotals will be internally consistent but discrepancies may be observed between tables cross-tabulating the same population by different variables. While randomisation compromises the table totals by making them appear inconsistent, this is the best available socio-demographic data at the suburb level. This level of compromise is not statistically significant and should not impact on decision makers making effective resource allocation and planning decisions.
No reliance should be placed on small cells as they are disproportionately impacted by random adjustment, respondent and processing errors.
Further information on confidentiality and random adjustment can be found in the Stats NZ fact sheet: 2006 Census confidentiality rules.