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Trend estimates help the user to identify the underlying magnitude and direction of a time series. Seasonal adjustment removes the effect of the last three listed influences from the data, leaving only trend and short-term irregular movements. Trend estimates are then obtained by removing the effects of the short-term irregularities, which in some series can be a major contributor to movements in the original data.
Trend estimates are produced by using a statistical procedure based on Henderson moving averages. At each time point in a series, a trend estimate is calculated using a centred x-term Henderson moving average of the seasonally adjusted series. The moving averages are centred on the point in time at which the trend is being estimated. The number of terms used to calculate the trend varies across surveys. Generally, ABS monthly surveys use a 13-term moving average and quarterly surveys use a 7-term moving average.
Estimates for the most recent time points cannot be calculated using the centred average method as there are insufficient data to do so. Instead, alternative approaches that approximate the smoothing properties of the Henderson moving average are used. This can lead to revision in the trend estimates for the most recent time periods until sufficient data are available to calculate the trend using the centred Henderson moving average. Revisions of trend estimates will also occur with revisions to the original data and re-estimation of seasonal adjustment factors.
Seasonal factors are reviewed at least annually for ABS labour series, to take account of additional original data. The results of the latest reviews were used to compile the trend estimates given in this publication. For further information about the most recent reviews of seasonal factors for the labour surveys, see the following publications:
The general methods used in the ABS for estimating trends are described in Information Paper: A Guide to Interpreting Time Series – Monitoring Trends (cat.no.1349.0).
RELIABILITY OF ESTIMATES
Estimates in this publication are subject to two types of error:
For more information on these sources of error, and on measures of these types of errors, including standard errors, refer to the main publications associated with each of the data series presented in this publication (see the relevant sections later in these Explanatory Notes). More information on standard errors applying to LFS estimates is contained in Information Paper: Labour Force Survey Standard Errors, 2005 (cat.no.6298.0). To assist users, a spreadsheet incorporating the revised standard error models using composite estimation is available from Labour Force Survey Standard Errors, Data Cube, Oct 2009 (cat.no.6298.0.55.001).
Estimates have been rounded and discrepancies may occur between sums of the component items and totals.
LABOUR FORCE SURVEY DATA
Description of the survey
The Labour Force Survey (LFS) provides extensive and timely information on the labour market activity of the usually resident civilian population of Australia aged 15 and over. The LFS is a component of the Monthly Population Survey (MPS), which includes the LFS and supplementary surveys.
Monthly Population Survey
The Monthly Population Survey (MPS) is a population survey based on a multi-stage area sample of private dwellings and list samples of discrete Indigenous communities and non-private dwellings (hospitals, hotels, motels, etc.), and covers about 0.45% of the population of Australia. The information is obtained from occupants of selected dwellings by interviewers, with the first interview conducted face-to-face and subsequent interviews over the telephone. Once selected, households are included for eight consecutive months before being replaced.
Labour Force Survey
The Labour Force Survey (LFS ) has been conducted since 1960, first as a quarterly collection and then monthly from February 1978. The content of the survey has remained broadly the same since its introduction, but is regularly updated to ensure that is is the most appropriate for the provision of accurate labour force statistics.
The LFS is designed primarily to provide estimates of key labour force statistics for the whole of Australia and, secondarily, for each state and territory. Further details about concepts and methods are presented in Labour Statistics: Concepts, Sources and Methods (cat.no.6102.0.55.001),
A supplementary topic was included with the Labour Force Survey for the first time in November 1961, and this concept has been gradually extended so that now, a majority of the months in each year include supplementary questions on one or more topics. Results from each supplementary survey topic are released separately.
The survey methodology does not differ greatly among the supplementary surveys, and in many aspects is the same as the LFS methodology. A list of topics covered in recent years is available from Find Out More > Related Publications. Further details about concepts and methods are presented in Labour Statistics: Concepts, Sources and Methods (cat.no.6102.0.55.001).
Multi-Purpose Household Survey
The Multi-Purpose Household Survey (MPHS) was introduced in 2004–05. This survey vehicle is designed to provide statistics annually for a number of small, self contained topics, including a number of labour related topics. Data for MPHS topics are collected each month over a financial year. A list of topics covered in recent years is available from Find Out More > Related Publications. Further details about concepts and methods are presented in Labour Statistics: Concepts, Sources and Methods (cat.no.6102.0.55.001).
Interviews are generally conducted during the two weeks beginning on the Monday between the 6th and 12th of each month, with questions relating to the week prior to the interview (the reference week).
Notes on data
From time to time, changes to survey methodology affect the time series produced. Some examples of changes to this survey are: new questions added to the LFS questionnaire in April 2001; and the introduction of telephone interviewing in 1996–97.
In February 2004 the definition of unemployed persons was changed to include all persons who were waiting to start work and were available to start in the reference week, with consequent revisions to data from April 2001 to January 2004. For further details, see Information Paper: Forthcoming Changes to Labour Force Statistics, 2003 (cat.no.6292.0).
In May 2007, an improved method of estimation, known as composite estimation, was introduced into the Labour Force Survey. In introducing this change the ABS revised unit record data from April 2001 to April 2007 based on the new estimation method. While estimates for periods prior to April 2001 are unrevised and were compiled using a different estimation method, no trend break was identified in the employed persons series. Also, no change was identified in the trend breaks in the unemployed persons and unemployment rate series which arose with the introduction of a redesigned survey form in April 2001. For further details, see Information Paper: Forthcoming Changes to Labour Force Statistics, 2007 (cat.no.6292.0).
Labour Force Survey estimates are calculated in such a way as to add up to independent estimates of the civilian population aged 15 years and over (population benchmarks). These population benchmarks are projections of the most recently released quarterly Estimated Resident Population (ERP) data. For information on the methodology used to produce the ERP see Australian Demographic Statistics Quarterly (cat.no.3101.0).
The ERP series are revised twice-yearly in the March and September quarter issues of Australian Demographic Statistics Quarterly (cat.no.3101.0), released in September each year, to incorporate more up to date information available for the population components. For further details, see article in Labour Force, Australia (cat.no.6202.0) entitled: Labour Force Survey Population Benchmarks in the September 2010 issue.
The estimation method used in the Labour Force Survey is Composite Estimation, which was introduced in May 2007. Composite Estimation combines data collected in the previous six months with current month's data to produce the current month's estimates, thereby exploiting the high correlation between overlapping samples across months in the Labour Force Survey. The Composite Estimator combines the previous and current months' data by applying different factors according to length of time in the survey. After these factors are applied, the seven months of data are weighted to align with current month population benchmarks. For details see Information Paper: Forthcoming Changes to Labour Force Statistics, 2007 (cat.no.6292.0).
Family relationship is not determined for all households and persons in scope of the LFS. This is due to a number of factors related to the scope and coverage of the LFS, as well as difficulties in determining family structure and characteristics. The survey questions used to determine family relationships are restricted to persons enumerated as usual residents of private dwellings. That is, the following persons are excluded:
From October 2008, the method of producing family estimates from the LFS included: an expanded scope to include households containing permanent members of the Australian defence forces; a wider range of families in the LFS sample contributing to the family estimates; and improving the weighting method by utilising independent population benchmarks (of persons and households), ensuring the estimates more closely reflected the Australian population. See Improvements to Family Estimates from the Labour Force Survey (cat. no. 6224.0.55.002).
Further information and data on the LFS
LFS estimates are published monthly in Labour Force, Australia (cat.no.6202.0). A series of time series spreadsheets are released at the same time as this publication under cat.no.6202.0.55.001. More detailed estimates are released, in electronic format, one week later, under cat.no.6291.0.55.001 for monthly data, or cat.no.6291.0.55.003 for quarterly data. All electronic data can be accessed via the ABS website at <http://www.abs.gov.au>. For details on the data available in the Labour Force standard products, see Labour Force Survey Standard Products and Data Item Guide (cat. no. 6103.0). Additional data are available on request.
For further information about the range of LFS products and services, and the concepts and methodology used in the LFS, refer to Information Paper: Changes to Labour Force Survey Products (cat.no.6297.0), Labour Statistics: Concepts, Sources and Methods (cat.no.6102.0.55.001), or contact Labour Market Statistics on Canberra (02)62527206.
WAGE PRICE INDEX DATA
Description of the survey
The Labour Price Index (LPI) measures change in the price of labour in the Australian labour market, unaffected by changes in the quality or quantity of work performed, i.e. it is unaffected by changes in the composition of the labour force, hours worked, or changes in characteristics of employees (e.g. work performance). In the LPI, index numbers are compiled for a range of wage and non-wage costs. Information about the wage price indexes has been released for each quarter since September 1997.
The reference period for the survey is the last pay period ending on or before the third Friday of the mid-month of the quarter.
For further information about the range of products and services relating to the Wage Price Index, and the concepts and methodology used, refer to Labour Price Index, Australia (cat.no.6345.0), Labour Price Index, Concepts, Sources and Methods (cat.no.6351.0.55.001), the associated time series spreadsheets available from the ABS website, or contact the Manager, Labour Price Index on Perth (08)93605151.
AVERAGE WEEKLY EARNINGS DATA
Description of the survey
The Survey of Average Weekly Earnings has been conducted quarterly since August 1981. Approximately 5,500 businesses contribute to the survey each quarter. The purpose of the survey is to measure average gross weekly earnings of employee jobs in Australia.
Average weekly earnings statistics represent average gross (before tax) earnings of employees and do not relate to average award rates nor to the earnings of the 'average person'. Estimates of average weekly earnings are derived by dividing estimates of weekly total earnings by estimates of number of employees. Changes in the averages may be affected not only by changes in the level of earnings of employees but also by changes in the overall composition of the wage and salary earner segment of the labour force.
The reference period for the survey is the last pay period ending on or before the third Friday of the middle month of the quarter. For non-weekly payrolls, businesses are asked to provide one week's portion.
For further information about average weekly earnings statistics and the concepts and methodology used refer to Average Weekly Earnings, Australia (cat.no.6302.0), and Labour Statistics: Concepts, Sources and Methods (cat.no.6102.0.55.001), or contact the Manager, Survey of Average Weekly Earnings on Perth (08)93605304.
INDUSTRIAL DISPUTES DATA
Description of the survey
The ABS has been collecting information about industrial disputes since 1913. The Industrial Disputes collection produces estimates of the number of industrial disputes (where ten or more working days are lost), employees involved, and working days lost.
The scope of the Industrial Disputes collection is restricted to employing businesses at which an industrial dispute has occurred. For this collection, industrial disputes are defined as work stoppages of ten working days or more. Ten working days are equivalent to the amount of ordinary time worked by ten people in one day, regardless of the length of the stoppage, e.g. 3,000 workers on strike for two hours would be counted as 750 working days lost (assuming they work an eight-hour day).
Effects on other establishments not directly involved in the dispute, such as stand-downs because of lack of materials, disruption of transport services, power cuts, etc. are not included in the scope of this collection.
The collection reference period is the calendar quarter.
For further information about industrial disputes statistics, and the concepts and methodology used, refer to the electronic publication Industrial Disputes, Australia (cat.no.6321.0.55.001), and Labour Statistics: Concepts, Sources and Methods (cat.no.6102.0.55.001), or contact the Manager, Industrial Disputes on Perth (08)9360 5159.
JOB VACANCIES DATA
Description of the survey
The current Job Vacancies Survey has been conducted since November 1983, with the exception of between August 2008 and August 2009 when the survey was temporarily suspended. It is a quarterly sample survey of approximately 5,000 employers. The survey produces estimates of the number of job vacancies in Australia.
The reference date for the survey is the third Friday of the middle month of the quarter.
For further information about the range of products and services relating to ABS job vacancies statistics, and the concepts and methodology used, refer to Job Vacancies, Australia (cat.no.6354.0), Labour Statistics: Concepts, Sources and Methods (cat.no.6102.0.55.001), the associated time series spreadsheets available from the ABS website, or contact the Manager, Job Vacancies Survey on Perth (08)93605373.
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