Nature of data
The statistics in this release are based on final external migration counts. They relate to the number of movements of travellers, rather than to the number of travellers – that is, the multiple movements of individual people during a given reference period are each counted separately.
Data for country groupings
As of December 2000, the country groupings used in this release are consistent with the New Zealand Standard Classification of Countries 1999 (NZSCC 1999). Prior to this date, country groupings were based on earlier versions of the NZSCC.
New Zealand resident short-term departures
The commentaries relating to New Zealand resident short-term departures are based on the data for the country of main destination – that is, the country where each departing person intended to spend most of his or her time while away from New Zealand.
Changes in traveller category
In the preparation of migration statistics, the classification of each passenger is primarily determined by the passenger's response, on the arrival or departure card, to the question on intended or actual length of stay/absence. If the person's intention changes during the trip, then they may also change their migrant 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 permanent and long-term (PLT) migrant on arrival, but is later classified as a short-term visitor on departure. This is known as migration category jumping. Data users should recognise the limitations inherent in the information supplied by travellers.
The statistics for short-term passenger movements by country (ie arrivals by country of last permanent residence and departures by country of main destination) are derived from a systematic random sample taken each month from arrival and departure cards, and are therefore subject to sampling errors. However, total counts for short-term arrivals and departures of overseas visitors and New Zealand residents are actual counts, which are not subject to sampling errors. Figures for PLT arrivals and departures are also actual counts and have no sampling errors.
All data in the Hot Off The Press tables are available through the INFOS database. Where feasible, the series identifiers are shown (see tables 1–5 and the footnotes for table 11). The series in tables 1, 2 and 3 are available back to January 1950, and the seasonally adjusted series in tables 4 and 5 are available back to January 1982. The seasonally adjusted migration series were all revised when new seasonal adjustment procedures were introduced in August 1998. Likewise, the seasonally adjusted figures from January 1996 onwards are now updated monthly.
Seasonally adjusted series
The purpose of seasonally adjusting a time series is to measure and remove the varying seasonal components (caused by regular events such as holidays) in the series. This makes the data for adjacent months more comparable. The X-12-ARIMA computer program is used to produce the seasonally adjusted estimates of migration. In addition, the seasonally adjusted figures are subject to revision each month. The size of these revisions is expected to be minimal, with the largest revisions occurring in the months immediately prior to the current month.
The change to a four-term school year in 1996 resulted in changes to the seasonal patterns of the New Zealand resident arrivals and departures series. As a result, the seasonal adjustment for the two series was unsatisfactory. To overcome this, a two-stage procedure was introduced in August 1998. The series prior to 1996 were seasonally adjusted separately and the values fixed, while the series from January 1996 onwards are now seasonally adjusted each month and revised if appropriate. Further information on the seasonally adjusted migration series, including information on the revision procedures, can be obtained from the Statistical Methods Business Unit, Statistics New Zealand, Christchurch, phone 03 964 8700, fax 03 964 8791.
Migration processing system
The current migration processing system, which incorporates scanning and image recognition technology, was first used to process the June 2004 arrival and departure cards. Classing (as overseas visitors, New Zealand residents or PLT migrants) and capture of the information required for the migration sample are done automatically for the majority of the cards. Operator intervention is only required for approximately one-tenth of the cards. The system is used only for the production of statistics.
Users should be aware of the changes to the processing system when comparing data for June 2004 onwards with data for earlier periods.
For more information, follow the link from the technical notes of this release on the Statistics NZ website.
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While care has been used in processing, analysing and extracting information, Statistics NZ gives no warranty that the information supplied is free from error. Statistics NZ shall not be liable for any loss suffered through the use, directly or indirectly, of any information, product or service.
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External Migration: March 2008 will be released on 21 April 2008