Weekly oil price monitoring

The Ministry of Business, Innovation and Employment carries out weekly monitoring of “importer margins” for regular petrol and automotive diesel. The weekly oil prices monitoring report is reissued each week with the previous week's data.

The Ministry revised its weekly oil price monitoring method in September 2015. For more information see the frequently asked questions [PDF 235KB].

New Zealand petrol and diesel retail prices presented here represent weekly average retail prices from Auckland, Hamilton, Wellington and Christchurch: the main port price. These prices from October 2006 onwards have been adjusted to account for the significant discounting activity (through loyalty schemes, shopper coupons and regional discounting) that has become increasingly common since about 2006, and are referred to as the discounted price.

The level of discount is estimated each quarter by comparing the quarterly average main port price to the quarterly average retail price collected by Statistics New Zealand as part of their Consumers Price Index (CPI) calculations. Statistics New Zealand compile this price series by surveying a selection of service stations in 12 regions of New Zealand, as well as collecting information about discounting from the major fuel retailers.

Find out more information about Statistics New Zealand’s CPI calculation method.

Since the Statistics New Zealand CPI data are not available for the current quarter, an Auto Regressive Integrated Moving Average (ARIMA) model is used to estimate the current quarter’s discount amount. When new CPI data are available, the previous quarter’s estimated discount factor will be revised with the actual figure.

The importer margin is the difference between the discounted price less duties, taxes, levies, the New Zealand Emissions Trading Scheme (ETS) and the importer cost. That is, the gross margin available to the retailers to cover domestic transportation, distribution and retailing costs, and profit margins.

The importer cost is the cost importing the fuel to New Zealand. It includes the cost of purchasing the fuel in Singapore, shipping it to New Zealand, insurance and losses, and wharfage and handling.

The purpose of this monitoring is to promote transparency in retail petrol and diesel pricing and is a key recommendation from the New Zealand Petrol Review [PDF 706KB].



Importer Margins up to the week ending 20 November 2015 (updated weekly)

Please note that the trend series’ in the following two charts (and the above CSV file) are calculated using a LOESS smoothing algorithm.

Note | The weekly average main port price series used to be a Saturday to Friday average. It is now a Monday to Sunday average. For this reason comparing the new weekly table with previously published data is not advised.

Regular petrol

[image] petrol.


[image] diesel.

Individual Price Components up to the week ending 20 November 2015 (updated weekly)

The following charts show the magnitude of the individual components of the discounted regular petrol and diesel retail prices over the last two years.

Regular petrol

[image] IPC petrol.


[image] IPC diesel.

Long-term trends in real Importer Margins up to June quarter 2015 (updated quarterly)

[image] Regular petrol and diesel importer's margin.

International comparison of retail petrol prices for OECD countries (updated quarterly)

[image] Quarterly comparison of premium unleaded petrol prices and taxes in OECD countries.

Daily Importer Margin charts

Charts of the daily variability of the importer margin on regular petrol and diesel are included at the above link. These data are provided to the Ministry by Hale and Twomey Ltd. Please note that the data in the above charts are calculated using undiscounted retail prices, and will therefore generally be at a higher level than the Ministry’s weekly importer margins. Care should be taken when comparing these series’.

Data sources

The data is sourced from:


All data are presented as non-weighted weekly averages and adjusted to NZ dollars as appropriate based on the prevailing exchange rate.

More information on importer margins and costs is published in the annual Energy in New Zealand publication. A detailed time-series of fuel duties, taxes and levies are available from the Energy Prices data table.

The costs associated with the ETS are provided by Hale & Twomey based on the prevailing carbon price from the New Zealand Carbon Market.



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