National Population Estimates: December 2011 quarter

Data quality

Period-specific information
This section contains information about data that has changed since the last release

General information
This section contains information that does not change between releases.

Period-specific information

Estimates of 'mean year ended' population available in Infoshare

This release no longer contains estimates of the resident population for the mean year ended. These estimates can be found in Infoshare, which is a free, online database to access time series data. Infoshare contains estimates of the resident population for the mean year ended, from September 1991 to the current quarter. To access the data, select the following categories from the Infoshare homepage:

Subject category: Population
Group: Demography Population Estimates.

Upcoming changes to national population estimates series in Infoshare

National population estimates are currently available under two different groups in Infoshare; Demography Population Estimates and Demography Age Estimates. These will be merged to form one group, Population Estimates, where age will be a selection variable. In addition, the as at and mean series will appear in one table, such that they will be available as a selection variable under Estimate Type. These changes will come into effect in mid-2012.

General information

Base population

The estimated resident population at 30 June 2006 forms the base population for deriving post-censal population estimates.

The estimated resident population of New Zealand at 30 June 2006 is the 2006 census usually resident count from the 2006 Census (held on 7 March 2006), updated for:

  • residents missed or counted more than once by the census (net census undercount)
  • residents temporarily overseas on census night
  • births, deaths, and net migration between census night and 30 June 2006
  • reconciliation with demographic estimates at ages 0–4 years.

Quarterly national population estimates from September 2006 onwards were derived by updating the estimated resident population at 30 June 2006 for births, deaths, and net migration during the following period.

Accuracy of the data

Official national population estimates give the best available measure of how many people usually live in New Zealand. However, uncertainty is inherent in the estimation process. Statistics NZ produces national population estimates using a component methodology, where the components of population change (births, deaths and international migration) are used to update a base population. There is some uncertainty associated with component data, particularly the estimate of international migration. Generally speaking, the uncertainty associated with population estimates increases as the estimates move further away from the base (starting point). Uncertainty also increases as population estimates are broken down by age and sex.

International migration estimates

International migration statistics are based on electronic arrival and departure records supplied to Statistics NZ for each international passenger. All arrivals and departures are processed so they can be allocated to one of three passenger types: overseas visitors, New Zealand-resident travellers, and permanent and long-term migrants. The net number of permanent and long-term migrants provide the estimate of international migration used in deriving the national population estimates. Uncertainty arises due to changes in passenger intentions; a person may change their intentions after their arrival or departure, which may mean the recorded passenger type becomes incorrect. Statistics NZ does not revise published statistics to adjust for such changes. As a result, the uncertainty associated with population estimates increases as the time period between the reference date of the base population and the date of the estimate increases.

Birth and death estimates

There is some uncertainty associated with birth and death data. Birth and death registrations are used to estimate the number of births and deaths that occurred during each quarter. Not all births and deaths that occur in a quarter are registered by the end of the quarter, and this delay in registration is taken into account when estimating birth and death occurrences in the current quarter.

Determining data accuracy

It is not possible to ascertain the accuracy of current national population estimates as no independent or authoritative measure of the resident population exists. 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.

Provisional and final estimates

Provisional and final estimates are produced for the resident population each quarter. Provisional estimates are produced for the information and media releases. This is the first public release of population estimates for a quarter and they are released within six weeks of the end of the reference quarter. The final estimates are derived when an extra quarter of detailed vitals data is available, about five months after the end of the reference quarter. Changes between the provisional and final estimates are most apparent at the younger and older age groups, due to delayed registrations of births and deaths.

Birth estimates

The final estimation for births that occurred in a quarter is less accurate, as births are not registered as closely to their occurrence as are deaths (around 5 percent of births are not registered either in the quarter of occurrence or in the subsequent quarter). The final estimation for quarterly births has a 95 percent confidence interval of ±500 (or about 3.5 percent, based on an average of 14,000 births per quarter).

Death estimates

The estimate of deaths that occurred in the reference quarter is taken as those deaths that were registered either in the reference quarter or in the subsequent quarter, and that occurred in the reference quarter. The provisional estimation for quarterly deaths has a 95 percent confidence interval of ±250 (or about 3.5 percent, based on an average of 7,000 deaths per quarter). This final estimation for deaths is very accurate as very few deaths are registered later than one quarter after their occurrence (about 1 death in a 1,000 is not).

Population clock

Statistics NZ's online population clock gives a real-time approximation of the estimated resident population of New Zealand. The population clock uses the latest quarterly estimated resident population, and estimates of the expected number of births, deaths, and net migration for the coming quarter. The settings for each component (births, deaths, and net migration) are derived by converting the quarterly estimated totals into a 'per minute' figure, making allowance for the number of days per quarter.

2006-base population estimates extended

Statistics NZ planned to produce 2006-base post-censal estimates until mid-2012. Following the cancellation of the 2011 Census of Population and Dwellings, 2006-base post-censal estimates will now be produced until mid-2014.

2013-base population estimates

The 2013 Census of Population and Dwellings will take place on Tuesday, 5 March 2013. The 2013 Census website (www.census.govt.nz) provides information about the census.

Population estimates based on the 2013 Census will be released from August 2014. In addition, all population estimates after 30 June 2006 will be revised following results from the 2013 Census. 

Rounding

All figures in this release were rounded independently. Estimates of the total population, natural increase, net migration, and broad age groups are rounded to the nearest 100. National population estimates of five-year age groups are rounded to the nearest 10.

All derived figures in this release were calculated using data of greater precision than that published.

More information

Information about the population estimates contains detailed information about the methods used to derive population estimates.

Liability

While care has been used in processing, analysing, and extracting data and information in this publication, Statistics NZ gives no warranty it is error-free and will not be liable for any loss or damage suffered by the use, directly or indirectly, of any information in this publication.

Timing of published data

Timed statistical releases are delivered using postal and electronic services provided by third parties. Delivery of these released may be delayed by circumstances outside the control of Statistics NZ. Statistics NZ accepts no responsibility for any such delays.

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