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Seasonally adjusted chain volume figures are calculated from seasonally adjusted figures expressed in the prices of the previous year. As with original data, the seasonally adjusted chain volume measures are benchmarked to annual original estimates. As a consequence, the seasonally adjusted chain volume measures sum to the corresponding annual original figures - unlike their current price counterparts.
A trend estimate is obtained by removing the irregular component from the seasonally adjusted series. For estimates in this publication, it is calculated using a centred 7-term Henderson moving average of the seasonally adjusted series. The procedure is designed to minimise distortions in the trend level, turning point shape and timing of turning points. Estimates for the three most recent quarters cannot be calculated using this centred average method; instead an asymmetric average is used. This can lead to revisions in the trend estimates for the last three quarters when data become available for later quarters, even if none of the original data for earlier quarters has changed.
The higher the 'irregular' component in a series, then the greater the likelihood that trend estimates for the latest quarters will be revised as more observations become available. However, it is important to note that this does not make the trend series inferior to the seasonally adjusted or original series. In fact, in such cases the effect of the irregular component on overall movements is likely to be even more in the seasonally adjusted and the original estimates than in the trend series.
Trend estimates for aggregates such as GDP are derived directly, rather than as the sum of components. As a result, the sum of the trend estimates of individual components of a particular aggregate will not sum to the overall trend estimate of the aggregate for the latest three quarters. This approach provides higher quality trend estimates for key aggregates, particularly GDP.
For more information about ABS procedures for deriving trend estimates and an analysis of the advantage of using them over alternative techniques for monitoring trends, see Information Paper: A Guide to Interpreting Time Series - Monitoring Trends, 2003 (cat. no. 1349.0) or contact Time Series Analysis by email at <Time.Series.Analysis@abs.gov.au>.
State and territory versus Australian series
For trend and seasonally adjusted series, the sum of the states and territories generally does not equal the corresponding estimate for 'total Australia', nor are the quarter-to-quarter movements identical. On a few occasions, these differences have been significant, particularly for the seasonally adjusted series. This reflects both the shorter span of data available for seasonal analysis at the state level and the fact that seasonal analysis is generally carried out at a more aggregated level than for the 'total Australia' series. The state and territory trend and seasonally adjusted series are less accurate than the Australian data. However, as the state and territory time series lengthen, the quarterly movements in the sum of the state estimates should more closely match those in the Australian series.
Measures of gross domestic product (GDP)
GDP is derived by three approaches: the income approach (I), the expenditure approach (E) and the production approach (P). A description of each approach is provided in the following paragraphs. While each measure should, conceptually, produce the same estimate of GDP, if the three measures are compiled independently using different data sources, then different estimates of GDP result. The ABS aligns the estimates of GDP annually by balancing them in supply and use tables. These tables have been compiled from 1994-95, up to the year preceding the latest complete financial year. Balancing in supply and use tables ensures that the same estimate of GDP is obtained from the three approaches. Annual estimates using the I, E and P approaches are identical for the years for which these tables are compiled. For years balanced using supply and use tables, quarterly GDP is benchmarked to annual GDP. However, the three estimates of GDP can be different for any given quarter. The annual GDP estimate produced by balancing using supply and use tables forms the benchmark for the production of quarterly GDP going forward. Quarterly GDP is compiled in chain volume terms using all three approaches. The headline measure of GDP is a simple average of the three separate measures. It is labelled GDP(A), with "A" denoting "average".
Prior to 1994-95 quarterly and annual estimates using each approach are based on independent sources, and there are usually differences between the I, E and P estimates. For these periods, a single estimate of GDP has been compiled. In chain volume terms, GDP is derived by averaging the chain volume estimates obtained from each of the three independent approaches. The current price estimate of GDP is obtained by reflating the average chain volume estimate by the implicit price deflator derived from the expenditure-based estimates.
As a result of the above methods:
Income approach (I)
GDP using the income approach is derived as the sum of compensation of employees, gross operating surplus, gross mixed income and taxes less subsidies on production and imports. Volume estimates are derived at the total GDP level by deflating current price estimates by the implicit price deflator from the expenditure approach.
Expenditure approach (E)
GDP using the expenditure approach is derived as the sum of all final expenditures, changes in inventories and exports of goods and services less imports of goods and services. Volume estimates are derived for each of the components as well as for their sum.
Production approach (P)
GDP using the production approach is derived as the sum of gross value added for each industry, at basic prices, plus taxes less subsidies on products. Basic values represent the amounts received by producers, including the value of any subsidies on products, but before any taxes on products. The difference between the sum over all industries of gross value added at basic prices, and GDP at market (or purchasers') prices, is the value of taxes less subsidies on products.
In this publication, only volume estimates compiled using the production approach have been shown. These estimates are derived by extrapolating annual volume measures using various indicators. The information necessary to compile comprehensive current price estimates using the production approach is not available quarterly.
Financial intermediation services
In the national accounts, estimates are made for the output of banks and similar institutions who produce services through the provision of deposit and loan services. Often there is no single explicit charge for these services and instead the relevant financial institutions set interest rates such that a service margin can be earned. Thus, interest rates on loans are higher than would otherwise be the case if there were no service element provided and interest rates on deposits are lower than would otherwise be the case.
In order to appropriately account for this service component the output produced by these financial institutions is shown as being consumed by Households (includes unincorporated enterprises and private non profit institutions serving households), Corporations, and General government. In the sector income accounts the effect of allocating the output to consuming sectors is that part of the interest flow is deemed a payment of service and the balance is shown as interest such that the net effect on saving is zero.
In interpreting the income accounts it is therefore necessary to regard the interest flow series as being a flow without a service element - i.e. a pure interest flow. In the case of loans the interest flow that is shown will be less than the observed interest payment made to the financial institution. In the case of deposits the interest flow that is shown will be greater than the observed interest payment made by the financial institution. For further information users should consult the Australian System of National Accounts: Concepts, Sources and Methods (cat. no. 5216.0).
In addition to the publications already mentioned, others of interest include:
Current publications and other products released by the ABS are freely available from the ABS website <https://www.abs.gov.au>, the website contains a link to the daily Release Advice which details products to be released in the weeks (months) ahead.
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