Reported revisions to CPI, 2011

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15 September 2011
Embargo: 11.30 am (Canberra time)
Reported revisions to CPI

On Wednesday, 14 September 2011, the ABS issued an information paper outlining a change that will be occurring when the 16th series CPI is released in the September quarter 2011, due out on Wednesday 26 October 2011. There has been some media reporting referring to revisions to the Consumer Price Index (CPI) by the Australian Bureau of Statistics (ABS). The All groups CPI (headline measure) has not been revised. The All groups CPI for the June quarter 2011 was 0.9% for the quarter, and 3.6% through the year.

The ABS produces, together with the quarterly headline CPI, a suite of related indexes that help users understand the pattern of inflationary pressures in the Australian economy. These indexes include the measures of underlying trend inflation (the Trimmed mean and Weighted median) that filter out the effects of unusual price movements, such as the effects of the recent Cyclone Yasi on the price of bananas. These underlying trend indexes are also seasonally adjusted to remove the effects of normal seasonal price variations such as occur with fruit, and are subject to revision each quarter.

The ABS emphasises that the unadjusted All groups CPI will continue to be the headline measure of inflation.

As part of its recent review of the CPI, the ABS has undertaken an investigation of price seasonality and will be improving the seasonal adjustment of the underlying trend indexes (the trimmed mean and weighted median) from the September quarter 2011 by adjusting for seasonality in the prices of a wider range of goods and services than had previously occurred.

The new and improved underlying trend indexes will be published on 26 October 2011, in conjunction with the regular release of the quarterly September quarter 2011 CPI. This will be the first release of the 16th series CPI, which will also incorporate new expenditure weights and an updated commodity basket reflecting the latest information on current household spending patterns obtained from the 2009/10 Household Expenditure Survey.

To assist users in understanding the new indexes, the ABS released on the 14th of September a preliminary new version of the previously published underlying trend indexes (the Trimmed mean and the Weighted median) incorporating the new seasonal adjustment method. These indexes have shown differences in recent underlying inflationary trends, from the previously published data. The results in the information paper are a preliminary analysis and are subject to revision when the September quarter 2011 CPI data are released. Moving to the new seasonal adjustment method will result in a greater than usual number of revisions to the historical Trimmed mean and Weighted median series when they are first published on the new basis in the September quarter 2011.

More information on the impacts of moving to the new seasonal adjustment method is available in Information paper: Seasonal adjustment of Consumer Price Indexes, 2011 (cat. no. 6401.0.55.003).

More information on other changes associated with the release of the 16th series CPI in the September quarter 2011 is available in the June quarter 2011 issue of Consumer Price Index, Australia (cat. no. 6401.0), and in an upcoming Information paper: Introduction of the 16th series CPI, Australia, September 2011 (cat. no. 6470.0) to be released on 22 September 2011.

FURTHER INFORMATION Media requests and interviews:
Corporate Communications 1300 175 070