Air transport and the NZ Consumers Price Index

Buried deep in the revamped Statistics New Zealand web site one can find using Infoshare NEW data series for international and domestic air transport prices, together with road, rail and sea passenger transport prices - look under Economic Indicators: Consumers Price Index: CPI Classes for New Zealand.

I am not sure precisely what of the many thousands of tariffs the statisticians are monitoring to come up with these series. With respect to domestic air travel Price Index News: July 2009 UPDATED does however state:

"The initial impact of a recent new entrant [Jetstar], offering passenger air transport services on several routes within New Zealand, including the main trunk routes between Auckland, Wellington and Christchurch, will be mostly reflected in the CPI for the June 2009 quarter. Domestic air transport prices are collected monthly, for travel the following month. For example, prices collected in mid-May for travel to be taken in mid-June are included in the May month for CPI purposes. As such, approximately two-thirds of the impact of the introduction will be shown in the June 2009 quarter, with the remainder in the September 2009 quarter. Of the domestic routes tracked for the CPI, flights between the three main centres carry between 50 and 60 percent of the expenditure weight of the domestic air transport index."