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Consumer price index

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The consumers price index (CPI) measures the rate of price change of goods and services purchased by households. The CPI all groups index is prepared quarterly. The food group is the only commodity group of the CPI for which an index is prepared each month.

The CPI measures the changing cost of purchasing a fixed basket of goods and services which represents the average expenditure pattern of New Zealand households at the index base period.

It is used as a measure of inflation, an indicator for monitoring economic and monetary policy, an indicator of the effect of price change on the purchasing power of households' incomes, as a means to adjust benefits, allowances and incomes, and as a price deflator.

Tradables are goods and services that are imported or that are in competition with foreign goods and services either in domestic or foreign. Non-tradables are goods and services that do not face foreign competition.

Prices are obtained by price collectors from retail outlets in 15 urban areas: Whangarei, Auckland, Hamilton, Tauranga, Rotorua, Napier-Hastings, New Plymouth, Wanganui, Palmerston North, Wellington, Nelson, Christchurch, Timaru, Dunedin and Invercargill.

Prices are collected weekly, monthly, quarterly or annually, depending on the expected frequency of price changes exhibited by the good or service. Weekly surveys are conducted for fresh fruit and vegetables, and motor fuels. Monthly surveys are limited to the following commodities: food, non-food groceries, electricity, gas, tobacco, alcoholic drinks, newspapers, Internet, cellphones, rental cars, and domestic and international air travel. Some items are monitored throughout the quarter, eg telephone call charges. Mortgage interest is also surveyed monthly but has been excluded from the CPI all groups calculations following a June 1999 review.