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4 The Retail Trade survey, like most ABS economic surveys, takes its frame from the ABS Business Register which is primarily based on registrations to the Australian Taxation Office's Pay As You Go Withholding (PAYGW) scheme (and prior to 1 July 2000 the Group Employer (GE) scheme). The frame is updated quarterly to take account of new businesses, businesses which have ceased employing, changes in employment levels, changes in industry and other general business changes. The estimates include an allowance for the time it takes a newly registered business to get on to the survey frame.
5 Businesses which have ceased employing are identified when the Australian Taxation Office cancels their PAYGW registration (or previously their GE registration). In addition, from July 1999, businesses which did not remit under the GE scheme for the previous five quarters were removed from the frame. A similar process will be adopted to remove businesses who do not remit under the PAYGW scheme. Updating the frame to take account of changes in employment levels and industry was introduced from the April 2000 reference month. The July 1999 and April 2000 changes resulted in a shift in the level of the Retail series. However, in both cases historic data have been revised to progressively phase in this shift of level. As a result of this process, month to month movements are not perceptibly affected.
CHANGES TO ABS BUSINESS REGISTER
6 The introduction of The New Tax System has a number of significant implications for ABS business statistics, and these are discussed in the information paper ABS Statistics And The New Tax System (ABS Cat. no. 1358.0). The replacement of the GE registration process by PAYGW registration resulted in a number of changes to most business survey frames. However, an adjustment has been made to the Retail Trade series so that these changes will not affect broader level estimates of level and movement.
7 From July 2002, the ABS will make further changes to business statistics including adopting a new units model and expanding the frames to include all units on the Australian Business Register, including non-employers. However, these non-employers will continue to be excluded from the scope of the Retail Trade survey. For further information see Information Paper: Improvements in ABS Economic statistics [Arising from The New Tax System] (Cat. no. 1372.0).
DEFINITION OF TURNOVER
8 Turnover includes retail sales; wholesale sales; takings from repairs, meals and hiring of goods (except for rent, leasing and hiring of land and buildings); and commissions from agency activity (e.g. commissions received from collecting dry cleaning, selling lottery tickets, etc.) and net takings from gaming machines etc. From July 2000, turnover includes GST.
9 Seasonally adjusted estimates are derived by estimating and removing systematic calendar related effects from the original series. In the Retail trade series, these calendar related effects are known as seasonal (e.g. increased spending in December as a result of Christmas) and trading day influences (arising from the varying length of each month and the varying number of Sundays, Mondays, Tuesdays, etc in each month). Each influence is estimated by separate seasonal and trading day factors which, when combined, are referred to as the combined adjustment factors.
10 The seasonally adjusted estimates also have an allowance for an Easter proximity effect, which is caused when Easter falls late in March or early in April. This effect, when present, is combined with the seasonal and trading day factors to form the combined adjustment factors. See the Appendix of the July 2001 issue of this publication for more information.
11 The Retail series uses a concurrent seasonal adjustment methodology to derive the combined adjustment factors. This means that data from the current month are used in estimating seasonal and trading day factors for the current and previous months. Concurrent seasonal adjustment replaced the forward factor methodology from the April 2000 reference month. For more information see Information Paper: Introduction of Concurrent Seasonal Adjustment into the Retail Trade Series (Cat. no.8514.0).
12 Concurrent adjustment can result in revisions each month to estimates for earlier periods. However, in most instances, the only noticeable revisions will be to the combined adjustment factors for the current month, the previous month and the same month a year ago. The following table shows how the combined adjustment factor for these months, at the total Australian Retail, hospitality and services level, evolved under the concurrent seasonal adjustment methodology. The table presents two different estimates of the combined adjustment factors. The first row gives the combined adjustment factors estimated following the last annual reanalysis in July 2001 using data up to and including the June 2001 reference month. The second row gives the most recent combined adjustment factors estimated and used in this month's calculation of the concurrent seasonally adjusted series.
13 The seasonal adjustment methodology is able to produce combined adjustment factors for future months. The latest factors for some future months are shown in the following table. While these factors represent the best current estimate, the actual factors used for estimating the seasonally adjusted estimates in these months will differ because they will incorporate subsequent month's data as it becomes available.
14 The seasonal and trading day factors are reviewed annually at a more detailed level than possible in the monthly processing cycle. The annual reanalysis will not normally result in significant changes. For Retail Trade, the results of the latest review are shown in the July issue each year.
15 In the seasonal adjustment process, both the seasonal and trading day factors evolve over time to reflect changes in spending and trading patterns. Examples of this evolution include the slow move in spending from December to January; and, increased trading activity on weekends and public holidays. The seasonally adjusted estimates still reflect the sampling and non-sampling errors to which the original estimates are subject.
16 As a result of the different treatment of Australian and State totals in the seasonal adjustment process, the Australian total for an industry group may not necessarily equal the sum of the State totals for that industry group.
17 The monthly trend estimates are derived by applying a 13-term Henderson moving average to the seasonally adjusted estimates (7-term for quarterly series). The Henderson moving average is symmetric, but as the end of a time series is approached, asymmetric forms of the moving average have to be applied. The asymmetric moving averages have been tailored to suit the particular characteristics of individual series and enable trend estimates for recent periods to be produced. Estimates of the trend will be improved at the current end of the time series as additional observations become available. This improvement is due to the combined effect of the concurrent seasonal adjustment methodology and the application of different asymmetric moving averages for the most recent six months (or three quarters). As a result of the improvement, most revisions to the trend estimates will be observed for the most recent six months (or three quarters).
18 Trend estimates are used to analyse the underlying behaviour of the series over time. As a result of the introduction of The New Tax System, a break in the monthly trend series has been inserted between June 2000 and July 2000. Care should therefore be taken in comparing the series over time. For more details refer to the Appendix in the December 2000 issue of this publication.
19 For further information on trend estimates, see A Guide to Interpreting Time Series - Monitoring ‘Trends’: an Overview (Cat. no. 1348.0) or contact the Assistant Director, Time Series Analysis on Canberra 02 6252 6345.
CHAIN VOLUME MEASURES
20 The chain volume measures of retail turnover appearing in the quarterly issue of this publication are annually reweighted chain Laspeyres indexes referenced to current price values in a chosen reference year (currently 1999-2000). The reference year will be updated in the June quarter publication each year. Each year’s data in the Retail chain volume series are based on the prices of the previous year, except for the quarters of the latest incomplete year (i.e. for the 2001-2002 financial year) which are based upon the 1999-2000 financial year. Comparability with previous years is achieved by linking (or chaining) the series together to form a continuous time series.
RELIABILITY OF ESTIMATES
21 There are two types of error possible in estimates of retail turnover:
Sampling error which occurs because a sample, rather than the entire population, is surveyed. One measure of the likely difference resulting from not including all establishments in the survey is given by the standard error, see below. Sampling error may be larger for the first month of each quarter, when some of the businesses in the sample are replaced by other businesses so that the reporting load can be spread across retailers.
Non sampling error which arises from inaccuracies in collecting, recording and processing the data. The most significant of these errors are: misreporting of data items; deficiencies in coverage; non-response; and processing errors. Every effort is made to minimise reporting error by the careful design of questionnaires, intensive training and supervision of interviewers, and efficient data processing procedures.
22 Seasonally adjusted and trend estimates and chain volume measures are also subject to sampling variability. For seasonally adjusted estimates, the standard errors are approximately the same as for the original estimates. For trend estimates, the standard errors are likely to be smaller. For chain volume measures, the standard errors may be up to 10% higher than those for the corresponding current price estimates because of the sampling variability contained in the prices data used to deflate the current price estimates.
23 To assist users in assessing the reliability of estimates, each data series has been given a grading of A to E. Where:
24 The table below provides an indicator of reliability for key retail turnover estimates.
ABS DATA AVAILABLE ON REQUEST
25 The Retail Survey Special Data Service provides additional retail trade statistics which include further State industry dissections through to ‘top ten’ industry reports. For more information, contact the Retail Trade Special Data Services manager on Canberra 02 6252 5220.
26 Current publications produced by the ABS are listed in the Catalogue of Publications and Products, Australia (Cat. no. 1101.0). The ABS also issues, on Tuesdays and Fridays, a Release Advice (Cat. no. 1105.0) which lists publications to be released in the next few days. The Catalogue and Release Advice are available on this site or from any ABS office.
SYMBOLS AND OTHER USAGES
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