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8750.0 - Building Activity, Australia: Dwelling Unit Commencements, Preliminary, Mar 2002  
Previous ISSUE Released at 11:30 AM (CANBERRA TIME) 19/06/2002   
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  • Explanatory Notes

INTRODUCTION

1 This publication contains preliminary estimates from the quarterly Building Activity Survey of the number of dwelling units commenced. More comprehensive updated results for the last two quarters will be available shortly in Building Activity, Australia (Cat. no. 8752.0).

2 The statistics were compiled on the basis of returns collected from builders and other individuals and organisations engaged in building activity. From the March quarter 2002, the quarterly survey consists of a sample survey of private sector residential building jobs valued at $10,000 or more and a complete enumeration of all such public sector residential building jobs. Estimates in respect of commencements of private sector dwellings and total dwellings are therefore subject to sampling variability. The relative standard errors for these estimates are shown on page 2. Also, some returns containing jobs not known to have commenced are not received in time for inclusion in these estimates. Allowance is made for a proportion of these jobs, based on past experience, to have commenced. Estimates in this issue are therefore subject to revision.

3 The use of sample survey techniques in the Building Activity Survey means that reliable estimates of the number of private sector dwelling commencements are generally available only at State, Territory and Australia levels. Although subject to higher relative standard errors, a range of sub-State estimates of dwelling commencements may be available. Reliable small area data are available for the Northern Territory, which has been completely enumerated since the June quarter 1991. Detailed data on Building Approvals, based on information reported by local government and other reporting authorities, are available for regions below State and Territory level from the Building Approval series compiled by the ABS.


DEFINITIONS

4 A building is defined as a rigid, fixed and permanent structure which has a roof. Its intended purpose is primarily to house people, plant, machinery, vehicles, goods or livestock. An integral feature of a building's design, to satisfy its intended use, is the provision for regular access by persons.

5 A dwelling unit is defined as a self-contained suite of rooms, including cooking and bathing facilities and intended for long-term residential use. Units (whether self-contained or not) within buildings offering institutional care, such as hospitals, or temporary accommodation, such as motels, hostels and holiday apartments, are not defined as dwelling units.

6 A residential building is defined as a building predominantly consisting of one or more dwelling units. Residential buildings can be either houses or other residential buildings.

  • A house is defined as a detached building predominantly used for long-term residential purposes and consisting of only one dwelling unit. Thus, detached granny flats and detached dwelling units such as caretakers' residences associated with non-residential buildings are defined as houses for the purpose of these statistics.
  • An other residential building is defined as a building which is predominantly used for long-term residential purposes and which contains (or has attached to it) more than one dwelling unit (e.g. includes townhouses, duplexes, apartment buildings, etc.).

These statistics present the number of dwelling units in other residential buildings (and not the number of buildings).

7 Conversions, etc. Dwelling units can also be created as part of alterations and additions to existing buildings (including conversions to dwelling units) and as part of the construction of non-residential buildings. Such dwelling units are referred to in this publication under the heading of Conversions, etc.

8 Commenced. A building is regarded as commenced when the first physical building activity has been performed on site in the form of materials fixed in place and/or labour expended (this includes site preparation but excludes delivery of building materials, the drawing of plans and specifications and the construction of non-building infrastructures, such as roads).

9 Ownership. The ownership of a building is classified as either public sector or private sector according to the sector of the intended owner of the completed building as evident at the time of approval. Residential buildings being constructed by private sector builders under government housing authority schemes whereby the authority has contracted, or intends to contract, to purchase the buildings on or before completion, are classified as public sector.


SEASONAL ADJUSTMENT

10 Seasonally adjusted building statistics are shown in tables 1 and 2. In the seasonally adjusted series, account has been taken of normal seasonal factors and the effect of movement in the date of Easter which may, in successive years, affect figures for different quarters.

11 Since seasonally adjusted statistics reflect both irregular and trend movements, an upward or downward movement in a seasonally adjusted series does not necessarily indicate a change of trend. Particular care should therefore be taken in interpreting individual quarter-to-quarter movements. Each of the component series shown has been seasonally adjusted independently. As a consequence, while the unadjusted components in the original series shown add to the totals, the adjusted components may not add to the adjusted totals. Thus, for example, the figures which can be derived by subtracting seasonally adjusted private sector dwelling units from the seasonally adjusted total dwelling units should not be used to represent seasonally adjusted public sector dwelling units.

12 As happens with all seasonally adjusted series, the seasonal factors are reviewed annually to take account of each additional year's data. For the Building Activity Survey, the results of the latest review are shown in the December quarter issue each year.


TREND ESTIMATES

13 Seasonally adjusted series can be smoothed to reduce the impact of the irregular component in the adjusted series. This smoothed seasonally adjusted series is called a trend estimate.

14 The trend estimates are derived by applying a 7-term Henderson moving average to the seasonally adjusted series. The 7-term Henderson average (like all Henderson averages) is symmetric but, as the end of a time series is approached, asymmetric forms of the average are applied. Unlike weights of the standard 7-term Henderson moving average, the weights employed here have been tailored to suit the particular characteristics of individual series.

15 While the smoothing technique described in paragraphs 13 and 14 enables trend estimates to be produced for recent quarters, it does result in revisions to the estimates for the most recent three quarters as additional observations become available. There may also be revisions because of changes in the original data and as a result of the re-estimation of the seasonal factors. For further information, see Information Paper: 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 6076.


ACKNOWLEDGMENT

16 ABS publications draw extensively on information provided freely by individuals, businesses, governments and other organisations. Their continued cooperation is very much appreciated: without it, the wide range of statistics published by the ABS would not be available. Information received by the ABS is treated in strict confidence as required by the Census and Statistics Act 1905.


RELATED PRODUCTS

17 Users may also wish to refer to the following publications which are available from ABS Bookshops:
  • Building Activity, Australia (Cat. no. 8752.0) - issued quarterly
  • Building Approvals, Australia (Cat. no. 8731.0) - issued monthly
  • Construction Work Done, Australia, Preliminary (Cat. no. 8755.0) - issued quarterly
  • House Price Indexes: Eight Capital Cities (Cat. no. 6416.0) - issued quarterly
  • Housing Finance for Owner Occupation, Australia (Cat. no. 5609.0)- issued monthly
  • Producer Price Indexes, Australia (Cat. no. 6427.0) - issued quarterly
  • Private Sector Construction Industry, Australia, 1996-97 (Cat. no. 8772.0)

18 Current publications and other products 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 products to be released in the next few days. The Catalogue and Release Advice are available from any ABS office.


ABS DATA AVAILABLE ON REQUEST

19 As well as the statistics included in this and related publications, the ABS may have other relevant data available on request. Inquiries should be made to the National Information and Referral Service on 1300 135 070.


SYMBOLS AND OTHER USAGES


ABS Australian Bureau of Statistics
n.a.not available
-nil or rounded to zero
. .not applicable


Where figures have been rounded, discrepancies may occur between sums of the component items and totals.


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