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International Travel and Migration: September 2011
Embargoed until 10:45am  –  21 October 2011
Data quality

Data source 

International travel and migration statistics are based on electronic arrival and departure records for each international passenger supplied to Statistics New Zealand by the New Zealand Customs Service. These electronic records include flight and passport details such as date of travel, date of birth, sex, and country of citizenship.

The New Zealand Customs Service also supplies Statistics NZ with arrival and departure cards completed by passengers. Additional detail such as country of residence and travel purpose is captured from these cards and added to the information from electronic records.

Arrival and departure cards are owned by Immigration New Zealand, and are used to administer numerous New Zealand laws in addition to the production of statistics. Statistics NZ captures information from the cards only for statistical purposes, and passes the cards to Immigration NZ after data capture is complete.

A copy of the arrival card (PDF, 84kb) is available on the New Zealand Customs Service website, and a copy of the departure card on the Statistics NZ website. These are for reference only.

Accuracy of the data 

Data collection

Statistics NZ scans every arrival and departure card, and uses image recognition technology to automatically recognise and code responses. Processing staff then manually capture any required information not captured automatically – as not every response can be clearly recognised by automated software.

The imaging system automatically determines all of the information required for around 9 in every 10 cards, meaning about 1 million records require manual completion each year.

Some response fields are required from every card. These include passport number and birth date, which are used to match each card with the corresponding electronic record containing flight and passport details. Some fields are only required for certain passenger types, or for a sample of passengers.

Changes in recorded passenger intentions

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.

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.

Sampling

Some fields are only collected for a sample of passengers. Data from the sample is used to estimate the characteristics of the full population. This still provides a good picture of the characteristics of travellers, while greatly decreasing the time and cost of capturing the data.

All figures for permanent and long-term migrants are actual counts (not derived from a sample). Arrival and departure totals for overseas visitors and New Zealand-resident travellers are also actual counts. More detailed data for overseas visitors and New Zealand-resident travellers, such as figures by country or travel purpose, are derived from a sample.

The sample ratios currently used are:

  • Overseas visitor arrivals: 1 in 16
  • Overseas visitor departures: 1 in 26
  • New Zealand-resident traveller arrivals: 1 in 26
  • New Zealand-resident traveller departures: 1 in 20.

Figures derived from a sample may contain sample error (a difference from the actual figure). Small numbers are more likely to contain a large sample error as a percentage of the actual figure, and should be used with caution.

Tables showing the sample errors for selected cell sizes are included in the Information about international travel and migration page on the Statistics NZ website.

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 periods more comparable.

The seasonal adjustment process for international travel and migration statistics uses Statistics NZ's standard seasonal adjustment package, X-12-ARIMA, with enhancements that allow the specification and adjustment of additional calendar effects. These include the number and type of trading days in the month (as more people generally arrive and depart on Friday, Saturday, and Sunday), and holiday periods, which have important effects on travel but can occur in different months each year (eg Easter can be in March or April).

Both monthly and quarterly seasonally adjusted series are available. The quarterly series are adjusted independently of the adjustments made to the monthly series. Hence, quarterly figures may not equal the sum of monthly seasonally adjusted figures.

Seasonally adjusted and trend data back to January 1996 are subject to revision each period. The size of these revisions is expected to be minimal, with the largest revisions occurring in the periods immediately before the current month or quarter. Data before January 1996 is not revised. This cut-off is used because of the change to a four-term school year in 1996, which resulted in changes to the seasonal patterns of the New Zealand-resident traveller series.

Interpreting the data

Passenger counts

The statistics in this release relate to the number of passenger movements to and from New Zealand, rather than to the number of people – that is, the multiple movements of individual people during a given reference period are each counted separately. For example, a New Zealand resident making five business trips overseas within a year would be counted as five arrivals and five departures.

Timing of published data 

Final international travel and migration statistics: released approximately three weeks after the end of the reference month. This delay is longer for December and January data due to the peak travel period coinciding with the Christmas and New Year holidays.

New Zealand and overseas port data: becomes available two working days after the international travel and migration release.

Provisional international travel statistics: normally released at 3pm every Friday on the Provisional international travel statistics web page. These show the latest weekly and four-weekly figures for visitor arrivals and New Zealand-resident traveller departures, including figures for 10 major source and destination countries. No further data is available until the monthly release of final statistics.  

Confidentiality

Statistics NZ releases statistics derived from arriving and departing passenger records. It does not release the records of individual passengers.  

More information

More information about international travel and migration is available on our website.

Liability

While all care and diligence 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 the information in this publication.

Timing

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

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This work is licensed under the Creative Commons Attribution 3.0 New Zealand licence. You are free to copy, distribute, and adapt the work, as long as you attribute the work to Statistics NZ and abide by the other licence terms. Please note you may not use any departmental or governmental emblem, logo, or coat of arms in any way that infringes any provision of the Flags, Emblems, and Names Protection Act 1981. Use the wording 'Statistics New Zealand' in your attribution, not the Statistics NZ logo.

 

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