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6203.0 - Labour Force, Australia, Feb 2001  
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Special Article - Seasonal Reanalysis of monthly Labour Force Survey Estimates (Feb, 2001)


(This article is taken from Labour Force Australia February 2001 ABS Cat. Number 6203.0)



INTRODUCTION

Each year, all seasonally adjusted and trend Labour Force Survey (LFS) estimates are reanalysed and revised back to February 1978 after the application of updated seasonal factors. Revisions resulting from the 2001 reanalysis were released electronically on 8 March 2001. This article explains the annual seasonal reanalysis process and the methodology for seasonal and trend series adjustment applied to LFS estimates.

The impact of the revisions is illustrated in the table at the end of this article, where the revised estimates are compared with previously published estimates for selected seasonally adjusted series.


SEASONAL REANALYSIS

Seasonal adjustment is a means of removing the estimated effects of regular seasonal variations from a time series of data, so that the effects of other influences on the series can be recognised more clearly. The seasonally adjusted estimates also reflect the sampling and non-sampling errors present in the original data.

As with all ABS seasonally adjusted series, seasonal factors are reviewed when estimates for the latest year become available. This process assesses possible changes in seasonality, taking into account the most recent year’s data, in order to derive the seasonal adjustment factors for the coming year and any revisions to seasonal factors for previous years.

Seasonally adjusted series

For Australia, seasonally adjusted estimates for employed persons are obtained by adding the following independently adjusted series for males and females:

  • aged 15 to 19 employed full time;
  • aged 20 and over employed full time; and
  • employed part time.

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:
  • aged 15 to 19 looking for full-time work;
  • aged 20 and over looking for full-time work; and
  • looking for part-time work.

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 34 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.

Trend series

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 becomes 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 32 and 33 of the Explanatory Notes for further information.

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 8 March and were subsequently included in the February 2001 issue of Labour Force, Australia, Preliminary (Cat. no. 6202.0) on 15 March 2001. Revised estimates from February 1978 to January 2001 are available on AusStats, floppy disk or as a special data service. Revised seasonal adjustment factors from February 1978 to March 2001 are available on floppy disk or as a special data service.

Other series

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.


FURTHER INFORMATION

For further information about revised labour force estimates, contact Kate Nielsen on 02 6252 6525 or email kate.nielsen@abs.gov.au.


TABLE 1. LABOUR FORCE REVISION, FEBRUARY 2001: DIFFERENCE BETWEEEN PREVIOUSLY PUBLISHED AND
REVISED SEASONALLY ADJUSTED ESTIMATES OF EMPLOYED PERSONS, UNEMPLOYED PERSONS, UNEMPLOYMENTRATE AND PARTICIPATION RATE

Employed Persons ('000)
Unemployed Persons ('000)

Previously Published
Revised
Difference (a)
Previously Published
Revised
Difference (a)

1999
January
8,678.3
8,686.6
8.4
707.5
705.9
-1.6
February
8,705.0
8,697.4
-7.6
700.0
701.5
1.5
March
8,715.8
8,718.4
2.7
696.3
694.0
-2.3
April
8,716.3
8,720.3
4.0
703.7
701.2
-2.5
May
8,719.8
8,726.1
6.3
698.8
699.8
1.0
June
8,778.2
8,779.7
1.5
682.9
675.2
-7.7
July
8,789.4
8,779.5
-9.9
659.3
671.1
11.8
August
8,820.8
8,816.0
-4.8
677.4
679.9
2.4
September
8,829.0
8,826.7
-2.2
693.7
692.9
-0.8
October
8,871.8
8,869.3
-2.6
675.8
677.2
1.5
November
8,872.8
8,875.5
2.7
645.9
645.0
-0.9
December
8,912.3
8,910.6
-1.7
672.3
670.2
-2.2
2000
January
8,903.4
8,914.8
11.4
654.8
653.2
-1.6
February
8,962.4
8,954.0
-8.5
643.5
645.6
2.1
March
8,970.7
8,973.8
3.0
661.8
658.7
-3.1
April
9,008.2
9,010.9
2.8
656.5
654.0
-2.5
May
9,020.3
9,028.7
8.4
652.1
652.9
0.8
June
9,042.0
9,043.7
1.7
643.0
633.7
-9.3
July
9,117.8
9,106.4
-11.4
609.7
620.9
11.2
August
9,141.8
9,135.1
-6.7
623.7
626.6
2.9
September
9,111.4
9,109.1
-2.3
613.5
611.9
-1.5
October
9,106.2
9,102.8
-3.4
615.4
616.9
1.5
November
9,047.1
9,052.1
5.0
637.1
635.8
-1.3
December
9,086.7
9,084.3
-2.3
643.2
641.1
-2.2
2001
January
9,083.2
9,096.1
12.9
648.9
647.4
-1.4

Unemployment Rate (%)
Participation Rate (%)

Previously
Published
Revised
Difference (a)
Previously
Published
Revised
Difference (a)

1999
January
7.5
7.5
-0.0
63.0
63.1
0.0
February
7.4
7.5
0.0
63.1
63.0
-0.0
March
7.4
7.4
-0.0
63.1
63.1
0.0
April
7.5
7.4
-0.0
63.0
63.0
0.0
May
7.4
7.4
0.0
62.9
63.0
0.0
June
7.2
7.1
-0.1
63.1
63.1
-0.0
July
7.0
7.1
0.1
63.0
63.0
0.0
August
7.1
7.2
0.0
63.2
63.2
-0.0
September
7.3
7.3
-0.0
63.3
63.3
-0.0
October
7.1
7.1
0.0
63.4
63.4
-0.0
November
6.8
6.8
-0.0
63.1
63.1
0.0
December
7.0
7.0
-0.0
63.5
63.4
-0.0
2000
January
6.9
6.8
-0.0
63.2
63.3
0.1
February
6.7
6.7
0.0
63.5
63.4
-0.0
March
6.9
6.8
-0.0
63.6
63.6
-0.0
April
6.8
6.8
-0.0
63.7
63.7
0.0
May
6.7
6.7
0.0
63.7
63.7
0.1
June
6.6
6.5
-0.1
63.7
63.6
-0.1
July
6.3
6.4
0.1
63.9
63.9
-0.0
August
6.4
6.4
0.0
64.1
64.0
-0.0
September
6.3
6.3
-0.0
63.7
63.7
-0.0
October
6.3
6.3
0.0
63.6
63.6
-0.0
November
6.6
6.6
-0.0
63.3
63.3
0.0
December
6.6
6.6
-0.0
63.6
63.5
-0.0
2001
January
6.7
6.6
-0.0
63.5
63.6
0.1

(a) Calculated on unrounded estimates




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