International Travel and Migration: November 2008

Technical notes

Nature of data

The statistics in this release are based on final international travel and migration counts. They relate to the number of passenger movements, rather than to the number of people – that is, the multiple movements of individual people during a given reference period are each counted separately.

Changes in passenger type

In the preparation of international travel and migration statistics, the passenger type (overseas visitor, New Zealand-resident traveller, or permanent and long-term (PLT) migrant) is primarily determined by the passenger's response, on the arrival or departure card, to the questions on where they live and their length of stay or absence. If the person's intention changes later during the trip, this passenger type may no longer be correct. For example, a person may come to New Zealand with the declared intention of settling permanently (PLT migrant), but in fact may return overseas after a few months (overseas visitor). Data users should recognise the limitations inherent in the information supplied by travellers.

Sampling accuracy

The statistics for short-term passenger movements by country (that is, overseas visitor arrivals by country of last permanent residence, and New Zealand-resident 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 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.

Infoshare and INFOS databases

All data in the Hot Off The Press tables are available through the Infoshare database (www.stats.govt.nz/infoshare), a free-of-charge online tool that gives you access to a range of time-series data. International travel and migration data are currently available through two subjects within Infoshare:

  • International travel and migration (under Tourism on the Browse page)
  • External migration (under Population on the Browse page).

The international travel and migration subject is under development, with more detailed cross-tabulations being progressively added. This will eventually replace the external migration subject, but both will remain available until development of the international travel and migration subject is complete.

Both subjects are also available in the INFOS database (for subscribers only). Where feasible, INFOS series identifiers are shown in the Hot Off The Press tables.

New Zealand resident short-term departures

The commentaries relating to New Zealand-resident short-term departures are based on data for the country of main destination – that is, the country where each departing person intended to spend most of their time while away from New Zealand.

Seasonally adjusted and trend series

The purpose of seasonally adjusting a time series is to measure and remove the varying seasonal components in the series (for example, there are more visitor arrivals during the New Zealand summer, due to the warmer weather and longer daylight hours). This makes the data for adjacent months more comparable. The X-12-ARIMA computer program is used to produce the seasonally adjusted estimates of key international travel and migration series. 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.

Processing system

The current international travel and migration processing system, which incorporates scanning and image recognition technology, was first used to process the June 2004 arrival and departure cards. The determination of passenger type (overseas visitor, New Zealand-resident traveller, or PLT migrant) and capture of the information required for the 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.

More information

For more information, follow the link from the technical notes of this release on the Statistics NZ website.

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