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Feature Article - Seasonal Reanalysis of Monthly Labour Force Survey Estimates (Feb 2002)
Original estimates of married females employed full time and employed part time are also independently seasonally adjusted, but are not used in the calculation of total female seasonally adjusted employment.
Seasonally adjusted estimates for unemployed persons are obtained by adding the following independently adjusted series for males and females:
Original data for males and females aged 15 to 19 looking for first full-time job are also seasonally adjusted, but are not used in the calculation of the aggregate estimates. The series for married females looking for full-time and part-time work are also independently adjusted, but are not used in the calculation of total female seasonally adjusted unemployment.
Seasonally adjusted estimates for the labour force are formed by adding the seasonally adjusted component series for the employed and unemployed. Seasonally adjusted unemployment rates are calculated using seasonally adjusted unemployment and labour force estimates. Seasonally adjusted participation rates are calculated using seasonally adjusted labour force and unadjusted population estimates. Seasonally adjusted unemployment to population ratios are calculated using seasonally adjusted unemployment and unadjusted population estimates.
For the States and Territories, seasonally adjusted estimates of employment and unemployment are obtained by the addition of the independently adjusted series for males and females. Estimates of males and females employed full time are also adjusted, but are not used to generate total employment estimates.
Given that estimates for Australia, States and Territories are adjusted independently, the addition of seasonally adjusted estimates across all States and Territories will not generally equal the seasonally adjusted Australian total. Seasonally adjusted estimates for the Northern Territory and the Australian Capital Territory are not published due to the high level of revision to these estimates after each seasonal reanalysis. See paragraph 41 of the Explanatory Notes for further information.
Seasonally adjusted estimates of long-term unemployment are obtained by independently adjusting the original series for males and females unemployed for 52 weeks and under 104 weeks; and the series for males and females unemployed for 104 weeks and over. Total long-term unemployment estimates are the aggregation of these component series.
The employed persons series for each ANZSIC Industry Division is independently seasonally adjusted. For this reason, the sum of seasonally adjusted employment estimates for Industry Divisions will not generally equal the seasonally adjusted estimate of total employment. For further information on the seasonal adjustment process, contact the Assistant Director, Time Series Analysis on 02 6252 6076.
Evolving seasonal patterns cause revisions to seasonal factors. If reanalyses were conducted more frequently than annual, the seasonal factors would stabilise sooner. The option of using more frequent seasonal reanalyses in Labour Force Survey statistics will be discussed with users in the months ahead.
Also, investigations are continuing into recent indications that variations in the start date of Labour Force Survey interviewing (particularly during the month of January) may have a slight impact on seasonal patterns in the data. If such an effect is able to be identified and reliably estimated, a correction may be incorporated in future seasonal reanalyses.
Smoothing the seasonally adjusted series produces a ‘trend’ series by reducing the impact of the irregular movements in the series. A trend series can be used to analyse the underlying behaviour of the series over time.
For monthly series, a 13-term Henderson-weighted moving average is applied to the seasonally adjusted series, for all months except the last six. The last six monthly trend estimates are obtained by applying surrogates of the Henderson average to the seasonally adjusted series, and are revised as later data become available. For quarterly series, a 7-term Henderson moving average is applied to the seasonally adjusted series, with surrogate weights for the current end of the time series. See paragraphs 39 and 40 of the Explanatory Notes for further information.
For the purpose of deriving trend estimates only, seasonally adjusted observations are modified prior to the application of the Henderson weights, in instances where there have been unusually large identified outliers.
Using the Henderson weights, trend series are produced corresponding to each of the component seasonally adjusted series identified above. Like their seasonally adjusted counterparts, aggregate level trend data are the addition of these component series. Trend unemployment rates are calculated by dividing trend unemployment by trend labour force estimates. Trend participation rates and unemployment to population ratios are derived by applying Henderson weights to the respective seasonally adjusted rate and ratio series.
RELEASE OF REVISED DATA
Revised seasonally adjusted and trend labour force data were released electronically on 7 March and were subsequently included in the February 2002 issue of Labour Force, Australia, Preliminary (Cat. no. 6202.0) on 14 March 2002. Revised estimates from February 1978 to January 2002 are available on AusStats, floppy disk or as a special data service. Revised seasonal adjustment factors from February 1978 to January 2003 are available on floppy disk or as a special data service.
For the LFS, only major National and State/Territory series are subject to seasonal and trend adjustment. Other LFS series can be adjusted on a consultancy basis by contacting the person listed below.
For further information about revised labour force estimates, contact Mark Webb on 02 6252 6525 or email firstname.lastname@example.org.
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