EXPLANATORY NOTES


INTRODUCTION

1 This product contains final experimental estimates of the Aboriginal and Torres Strait Islander (Indigenous), non-Indigenous and total populations of Australia at 30 June 2006, based on results of the 2006 Census of Population and Housing.

2 Estimates are disaggregated by age and sex for states/territories, Remoteness Areas and Indigenous Regions. Estimates for Statistical Local Areas are available for total all ages only.


ESTIMATED RESIDENT POPULATION

3 Estimated resident population (ERP) is the official measure of the population of Australia, based on the concept of usual residence within Australia. Usual residence is that place where each person has lived or intends to live for six months or more from the reference date for data collection.

4 The estimates of the Indigenous and non-Indigenous populations presented in this publication are experimental. The estimates are based on 2006 Census of Population and Housing counts of Aboriginal and Torres Strait Islander Australians adjusted for net undercount as measured by the Post Enumeration Survey. The extent of undercoverage of Aboriginal and Torres Strait Islander Australians in the 2006 census and the relatively small sample size of the Post Enumeration Survey to adjust for that undercoverage means the estimates should be interpreted with caution. For more information on data quality see paragraphs 9 to 22 of the Explanatory Notes and Technical Note: Estimated Aboriginal and Torres Strait Islander Australian Resident Population - Method of Calculation.


INDIGENOUS STATUS

5 The Indigenous population of Australia comprises people who are of Aboriginal origin, Torres Strait Islander origin or both Aboriginal and Torres Strait Islander origin. The Commonwealth definition of an Aboriginal or Torres Strait Islander person is:

• a person of Aboriginal or Torres Strait Islander descent who;
• identifies as being of Aboriginal or Torres Strait Islander origin and who is;
• accepted as such by the community with which the person associates.

6 The 2006 Census of Population and Housing (Household Form) asked the following question of each person:

METHOD OF ESTIMATION

7 Estimated resident population by Indigenous status are compiled using census, Post Enumeration Survey (PES) and other demographic information. Starting with census counts by place of usual residence, a number of steps are involved. These include:

• Imputation of Indigenous status for census records with unknown Indigenous status (as a result of either non-response to the Aboriginal and Torres Strait Islander origin question in the census, or unknown Indigenous status on census records imputed by the Australian Bureau of Statistics (ABS) when a form could not be obtained from occupied dwellings identified in the field);
• An allowance for net census undercount: in a complex exercise such as the census, it is inevitable that some people will be missed and some will be included more than once. The PES, conducted three weeks after census night, collects information about where people were on census night and their characteristics to estimate net census undercount;
• An estimate of the number of Australian residents temporarily overseas at the time of the census;
• Backdating from the census date of 8 August 2006 to the ERP reference date of 30 June 2006 using data on births, deaths, and interstate and overseas migration for the intervening period;
• Minor demographic adjustments designed to address any anomalies in age and sex composition.

8 For further information, see Technical Note: Estimated Aboriginal and Torres Strait Islander Australian Resident Population - Method of Calculation.


DATA QUALITY

Census

9 The ABS aims to produce high quality data from the census. To achieve this, extensive effort is put into census form design, collection procedures, and processing procedures. There are four principle sources of error in census data: partial response, processing error, respondent error and undercount.

10 Partial response: When completing their census form, some people do not answer all the questions which apply to them. While questions of a sensitive nature are generally excluded from the census, all topics have a level of non-response. However, this level can be measured and is generally low. In those instances where a householder fails to answer a question, a not stated code is allocated during processing, with the exception of non-response to age, sex, marital status and place of usual residence. These variables are needed for population estimates, so they are imputed using other information on the census form, as well as aggregate data from the previous census.

11 Processing error: The processing of information from census forms is now mostly automated, using scanning, Intelligent Character Recognition and other automatic processes. Quality assurance procedures are used during census processing to ensure processing errors are kept at an acceptable level. Sample checking is undertaken during coding operations, and corrections are made where necessary.

12 Respondent error: The census form may be completed by one household member on behalf of others. Incorrect answers can be introduced to the census form if the respondent does not understand the question or does not know the correct information about other household members. Many of these errors remain in the final data.

13 Undercount: The goal of the census is to obtain a complete measure of the number and characteristics of people in Australia on census night and their dwellings, but it is inevitable that a small number of people will be missed and some will be counted more than once. In Australia, more people are missed from the census than are counted more than once. The net effect when both factors are taken into account is an undercount.

14 Each of these sources of error are particularly relevant to, and have the potential to significantly impact on, the census counts of Aboriginal and Torres Strait Islander Australians.

15 Further information on census data quality is available in Census Dictionary, 2006 (cat. no. 2901.0) and 2006 Census Data Quality Working Papers, available on the ABS web site www.abs.gov.au/census.


The Post Enumeration Survey (PES), sampling error and undercount

16 Due to the uncertainty in Indigenous census counts as well as the method of estimating net undercount of the Indigenous population, estimates presented in this product should be interpreted with caution.

17 The ABS conducts the PES shortly after the census to determine how many people were missed in the census and how many were counted more than once. The design of the survey is such that estimates of net undercount are suitable for augmenting census counts for the purpose of deriving population estimates for Australia and the states and territories. For 2006, the survey had a sample size of around 40,000 households across Australia.

18 As estimates of undercount are based on a sample survey they are subject to sampling error. Since only a sample of dwellings is included in the PES, estimates derived from the survey may differ from figures which would have been obtained if all dwellings had been included in the survey. One measure of the likely difference is given by the standard error (SE) which indicates the extent to which an estimate might have varied by chance because only a sample was included. The relative standard error (RSE) is the standard error expressed as a percentage of the estimate to which it refers.

19 For Australia, the direct estimate of the Indigenous population obtained from the PES was 513,977 persons, with a standard error of 13,309 (a relative standard error (RSE) of 2.6%).

20 For the states and territories, the preliminary estimates obtained from the PES of the census night population (referred to as the 'PES estimate') were subject to high RSEs (ranging from 3.5% for the NT to 7.3% for WA). A study has been subsequently undertaken to examine methodologies that would result in more reliable estimates. The outcome of the study was that an Empirical Bayes method has been adopted for compiling the final estimates.

21 The PES sample is insufficient to produce estimates of net undercount by Indigenous status at the sub-state/territory level. Undercount was therefore apportioned to Statistical Local Areas based on age, sex, Indigenous status and state/territory.

22 It is important to note that at the sub-state/territory level, differences between census counts and estimates of the Indigenous population are not indicative of, nor should be interpreted as, the true level of undercount; rather, these differences are a by-product of the assumptions that contribute to the estimation process.

23 For further information see Technical Note: Estimated Aboriginal and Torres Strait Islander Australian Resident Population - Method of Calculation.

24 For further information on the Post Enumeration Survey see Census of Population and Housing - Undercount, 2006 (cat. no. 2940.0), Information Paper: Measuring Net Undercount in the 2006 Population Census, 2007 (cat. no. 2940.0.55.001), Research Paper: An Estimating Equation Approach to Census Coverage Adjustment, May 2007 (cat. no. 1351.0.55.019) and Census of Population and Housing - Details of Undercount, Aug 2006 (cat. no. 2940.0).


AUSTRALIAN STATISTICAL AREAS

25 This publication contains data presented according to a number of geographic classifications: the Main Structure of the Australian Standard Geographical Classification (ASGC), Remoteness Areas (RA) and the Australian Indigenous Geographical Classification (AIGC).


Australian Standard Geographical Classification - Main Structure

26 Under the Main Structure of the Australian Standard Geographical Classification, statistical areas are defined in ascending order as follows:

• Statistical Local Areas (SLAs): These areas are, in most cases, identical with, or have been formed from a division of, whole Local Government Areas (LGAs). In other cases they represent unincorporated areas. In aggregate, SLAs cover the whole of a state or territory without gaps or overlaps. In some cases legal LGAs overlap Statistical Subdivision boundaries and therefore comprise two or three SLAs (Part A, Part B and, if necessary, Part C).
• Statistical Subdivisions (SSDs): These are of intermediate size, between SLAs and Statistical Divisions (SDs). In aggregate, they cover the whole of Australia without gaps or overlaps. They are defined as socially and economically homogeneous regions characterised by identifiable links between the inhabitants. In non-urban areas an SSD is characterised by identifiable links between the economic units within the region, under the unifying influence of one or more major towns or cities.
• Statistical Divisions (SDs): These consist of one or more SSDs. The divisions are designed to be relatively homogeneous regions characterised by identifiable social and economic units within the region, under the unifying influence of one or more major towns or cities. There were some major changes made to the SD structure in south-east Queensland in the 2006 edition of the ASGC.
• State/territory (S/T): The state/territory is the largest spatial unit in the Main Structure and in the ASGC. Six states and five territories are recognised in the ASGC: New South Wales, Victoria, Queensland, South Australia, Western Australia, Tasmania, Northern Territory, Australian Capital Territory, Jervis Bay Territory and the External Territories of Christmas Island and Cocos (Keeling) Islands.

27 In this publication, Jervis Bay Territory, Christmas Island and Cocos (Keeling) Islands are collectively referred to as 'Other Territories' and are included in totals for Australia.

28 For further information see Australian Standard Geographical Classification (ASGC), Jul 2006 (cat. no. 1216.0).


Remoteness Areas

29 Remoteness Areas (RA) are the spatial units that make up the ASGC Remoteness Classification. There are six classes of Remoteness Area in the Remoteness Structure: Major Cities of Australia, Inner Regional Australia, Outer Regional Australia, Remote Australia, Very Remote Australia and Migratory.

30 Within a state/territory, each RA represents an aggregation of non-contiguous geographical areas which share common characteristics of remoteness.

31 While statistical data classed to this structure may be available by state/territory, characteristics of remoteness are determined in the context of Australia as a whole. Therefore, not all RAs are represented in each state/territory.

32 For further information see Australian Standard Geographical Classification (ASGC), Jul 2006 (cat. no. 1216.0).


Australian Indigenous Geographical Classification

33 Data are also presented according to the Australian Indigenous Geographical Classification (AIGC) which refers to boundaries as defined at 1 July 2006. Under this classification, areas are defined as follows:

• Indigenous Regions (IREG): The Australian Government uses 30 Indigenous Coordination Centres (ICC) and the Torres Strait Regional Authority (TSRA) to manage the delivery of a range of services to Aboriginal and Torres Strait Islander peoples across Australia. For census purposes, the ABS defines Indigenous Regions based on ICC and TSRA areas. In aggregate, IREGs cover the whole of Australia without gaps or overlaps.

34 For further information see Maps and Census Profiles, Australian Indigenous Geographical Classification, 2006 (cat. no. 4706.0.30.001).


CONFIDENTIALITY

35 The Census and Statistics Act, 1905 provides the authority for the ABS to collect statistical information, and requires that statistical output shall not be published or disseminated in a manner that is likely to enable the identification of a particular person or organisation. This requirement means that the ABS must take care that identifiable information about individual respondents cannot be derived from published data.

36 To protect confidentiality within this publication, some small cell values have been adjusted. No reliance should be placed on cells with small values.

37 In addition, some Remoteness Areas in the states and territories have been combined to protect confidentiality. In Victoria, Outer Regional Australia and Remote Australia have been combined to produce Balance of Victoria. In Tasmania, Outer Regional Australia, Remote Australia, and Very Remote Australia have been combined to produce Balance of Tasmania. Remoteness Areas are not available for the ACT in this product.


FURTHER INFORMATION

Related publications and references

38 Other ABS publications that may be of interest to users of this product include:

• Australian Demographic Statistics (cat. no. 3101.0)
• Australian Historical Population Statistics (cat. no. 3105.0.65.001)
• Births, Australia (cat. no. 3301.0)
• Census Dictionary, 2006 (cat. no. 2901.0)
• Census of Population and Housing - Details of Undercount, Aug 2006 (cat. no. 2940.0)
• Census of Population and Housing - Undercount, 2006 (cat. no. 2940.0)
• Deaths, Australia (cat. no. 3302.0)
• Demography Working Paper 2001/4 - Issues in Estimating the Indigenous Population, 2001 (cat. no. 3126.0)
• Demography Working Paper 2004/3 - Calculating Experimental Life Tables for Use in Population Estimates and Projections of Aboriginal and Torres Strait Islander Australians (cat. no. 3106.0.55.003)
• Experimental Estimates of the Aboriginal and Torres Strait Islander Population, 1991 to 1996 (cat. no. 3230.0)
• Experimental Estimates and Projections, Aboriginal and Torres Strait Islander Australians, 1991 to 2009 (cat. no. 3238.0)
• Experimental Projections of the Aboriginal and Torres Strait Islander Population, 1996 to 2006 (cat. no. 3231.0)
• Information Paper: Measuring Net Undercount in the 2006 Population Census, 2007 (cat. no. 2940.0.55.001)
• Occasional Paper: Population Issues, Indigenous Australians, 1996 (cat. no. 4708.0)
• Population Characteristics, Aboriginal and Torres Strait Islander Australians, 2006 (cat. no. 4713.0)
• Population Distribution, Aboriginal and Torres Strait Islander Australians, 2006 (cat. no. 4705.0)
• The Health and Welfare of Australia's Aboriginal and Torres Strait Islander Peoples, 2008 (cat. no. 4704.0)

39 Current publications and other products released by the ABS are listed on the ABS web site www.abs.gov.au.

40 As well as the statistics included in this and related publications, additional information is available from the ABS web site at www.abs.gov.au and accessing Themes/Demography.

41 Related publications and articles which may also be of interest are:

• The Aboriginal Population of Australia, Smith, L.R., Australian National University Press, Canberra (1980).