CHANGES IN THIS AND FUTURE ISSUES
CHANGES TO SAMPLING AND SEASONAL ADJUSTMENT
The sampling scheme used for the statistics in this publication has changed. The Australian Statistician announced on 4 November 2008 that the full monthly sample would be reinstated to the Retail Business Survey. As a result, the sample size for the November 2008 survey was increased from 900 to 2700 businesses. Obtaining turnover from businesses in the increased sample size each month will reduce the volatility in the month to month estimates.
In conjunction with the increased monthly sample size, the seasonally adjusted series were reanalysed. Industry group totals had been directly seasonally adjusted from July 2008. With the availability of the more detailed monthly data, the industry group totals are indirectly seasonally adjusted from the November 2008 issue i.e. the industry sub-groups are directly seasonally adjusted and the industry totals derived from this more detailed data. In addition, forward seasonal factors (based on the series up to June 2008) are being used instead of concurrent seasonal adjustment to avoid the seasonal factors being distorted by the increased volatility in the original estimates from July to October 2008.
Due to the use of forward factors, published seasonally adjusted series will not be revised as data for additional months become available. Published seasonally adjusted series for a particular month will only be revised if the original series for that month is revised.
Estimates for October 2008 are based on a sample size of 900 businesses and therefore movements between October and November 2008 reflect a higher level of volatility (see Interpreting Monthly Movements section under Main Features). For this reason this issue continues to focus on trend estimates.
An information paper Changes to the Dissemination of Retail Trade Statistics, January 2009 (cat. no. 8501.0.55.005) is scheduled for release on 21 January 2009. This paper will summarise changes to be made to the dissemination of Retail Trade statistics from the December 2008 issue as a result of the reinstatement of the full monthly sample. The paper will advise the timing of the proposed changes and provide access, via the ABS website, to shell records of the spreadsheets. With the changes being made to this publication, the December quarter 2008 issue of Retail Trade Quarterly Indicators (cat. no. 8502.0) will be the final release.