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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:
8 For further information, see Technical Note: Estimated Aboriginal and Torres Strait Islander Australian Resident Population - Method of Calculation.
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:
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).
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:
34 For further information see Maps and Census Profiles, Australian Indigenous Geographical Classification, 2006 (cat. no. 4706.0.30.001).
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.
Related publications and references
38 Other ABS publications that may be of interest to users of this product include:
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:
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