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Sampling error occurs when a sample or subset of the population is surveyed rather than the entire population. One measure of the likely difference resulting from not including all of the population in the survey is given by the standard error. While the selection of employers and employee jobs are based on sampling techniques, standard errors are not available for the wage price index. While it is reasonably straightforward to calculate sampling errors for a level estimate such as the total number of employees jobs, it is not so straightforward to determine standard errors for the WPI which uses both sampling and index methodologies.
Original index numbers are released as final figures at the time they are first published. Revisions have never occurred and will only occur in exceptional circumstances. Trend and seasonally adjusted indexes are revised as extra quarters are included and seasonal factors are updated.
The methodology used to construct the WPI is similar to that used for other price indexes produced by the ABS such as the Consumer Price Index and the Producer Price Indexes. The sample for the WPI, is selected from the ABS Business Register which is primarily based on registrations to the Australian Taxation Office's Pay As You Go Withholding scheme.
Employers are classified to an industry using the Australian and New Zealand Standard Industrial Classification (ANZSIC) 2006 (cat. no. 1292.0). Up until June quarter 2009, the content and format of tables containing industry data reflected the 1993 version. Indexes for previous periods have been reproduced on an ANZSIC 2006 basis by reclassifying the businesses that reported data in earlier periods to the appropriate industry division of ANZSIC 2006. Index movements for Australia, state/territory, sector and All industries original series were not affected by the introduction of the new industry classification. Details about the change to ANZSIC 2006 are outlined in Information Paper: Update on ANZSIC 2006 Implementation for the Labour Price Index, Australia 2009 (cat. no. 6345.0.55.001).
The ABS conducts a number of sample surveys of businesses which collect information about wages and salaries. One of these series, Survey of Average Weekly Earnings (AWE), is designed to measure the level of average earnings in Australia at a point in time. Period to period movements for the AWE series are not comparable with those from the wage price index. The two series have different purposes. Consequently, they have different concepts, and use different sample selection and estimation methodologies.
The WPI publication (cat. no. 6345.0) contains Explanatory Notes, Appendices and a Glossary that provide information about data sources, terminology and other technical aspects of the series. More detailed information can also be found in the Wage Price Index, Concepts, Sources and Methods (cat. no. 6351.0.55.001).
The total hourly rates of pay excluding bonuses index Australia and sector level indexes are the only indexes of the WPI that are seasonally adjusted.
Additional wage price indexes are available on request. To make enquiries about such data, telephone WPI on Perth (08) 9360 5151 or email <email@example.com>
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