International Passenger Survey

Introduction of new airports into the International Passenger Survey sample

Since 2001 there has been a considerable increase in traffic through airports in the UK. Consequently, Liverpool and Prestwick were introduced into the International Passenger Survey sample at the beginning of 2005. Between 2000 and 2004 traffic through Liverpool quadrupled to over two and half million international passengers. At Prestwick there was a fivefold increase to nearly one and half million passengers over the same period.

Modification to IPS system of calculating weights for contacts at UK regional airports

In order to ensure future IPS results are compatible with previously published information, the part or the IPS weighting system which deals with UK residual airports is to be modified. A discontinuity in regional results would otherwise occur due to the introduction of Prestwick and Liverpool airports into the IPS sample in January 2005. The change relates to the way traffic from airports not sampled by the IPS (about 5% of all international traffic to and from the UK) is accounted for. Further information regarding the change can be obtained by e-mailing ips@ons.gov.uk.

Reasons for Changes

Examination of the provisional results for 2005 has shown a higher then expected rise in results for Scotland which was in part due to the introduction of Prestwick and Liverpool airports into the IPS sample from January 2005 and in part to the way traffic from un-sampled airports was accounted for.

The IPS weighting processes were reviewed and a modified system for dealing with traffic from un-sampled airports developed which was approved by both the ONS methodology unit (which ensures changes in methodology are sound) and the IPS steering group (which represents all the major IPS clients and users). The new methodology prevents overestimates of traffic volumes to any particular UK region and additionally it prevents changes in traffic at remote locations in, for example, the south from affecting results in Scotland, and visa versa.

This page last revised: Wednesday, 12 July 2006