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6 The 2011 Census of Population and Housing (Household Form) asked the following question of each person:
METHOD OF ESTIMATION
7 Estimated resident populations 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 Resident Aboriginal and Torres Strait Islander Australian 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 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, some will be counted more than once and some will not be identified correctly. 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, 2011 (cat. no. 2901.0) and 2011 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 Aboriginal and Torres Strait Islander Census counts as well as the estimation of net undercount of the Aboriginal and Torres Strait Islander population, estimates presented in this product should be interpreted with a degree of 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 2011, the survey had a sample size of around 43,000 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 Aboriginal and Torres Strait Islander population obtained from the PES was 662,300 persons, with a standard error of 14,300 (and a relative standard error (RSE) of 2.2%). For estimating the Aboriginal and Torres Strait Islander population of states and territories, undercount estimates were adjusted to improve the reliability of estimates. For more information on the method applied, see Technical Note: Estimated Resident Aboriginal and Torres Strait Islander Australian Population - Method of Calculation. Unadjusted undercount rates are presented below but should be used for illustrative purposes only. The adjusted estimates which were actually used in the calculation of final Aboriginal and Torres Strait Islander population estimates and which should be used can be found in Technical Note: Estimated Resident Aboriginal and Torres Strait Islander Australian Population - Method of Calculation.
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 Areas Level 2 based on age, sex, Indigenous status and state/territory. For further information on this process, please refer to Regional Population Grow, Australia, 2011 (cat. no. 3218.0)
22 It is important to note that at the sub-state/territory level, differences between Census counts and estimates of the Aboriginal and Torres Strait Islander population should not be interpreted as a definitive measure of the actual level of undercount; rather, these differences are a by-product of the assumptions that contribute to the estimation process, and the differences should be considered indicative, based on the best available (though limited) information.
23 For further information see Technical Note: Estimated Resident Aboriginal and Torres Strait Islander Australian Population - Method of Calculation.
24 For further information on the Post Enumeration Survey see Census of Population and Housing - Details of Undercount, 2011 (cat. no. 2940.0).
AUSTRALIAN STATISTICAL AREAS
25 This publication contains data coded to a number of statistical geographic structures within the statistical geography classification called the Australian Statistical Geography Standard (ASGS). The structures used are: the Main Structure, the Remoteness Structure and the Indigenous Structure.
26 Users should note that the Australian Statistical Geography Standard (ASGS) became effective in July 2011. It replaces the previously used Australian Standard Geographical classification (ASGC) and differs in the fact that the ASGS is more stable, the regions are more consistent in population size, are designed to give the maximum geographical detail for a range of published data, and represent underlying settlement patterns and socio-economic relationships. Information on the new standard is available on the ABS website under 'Statistical Geography'. Alternatively, see Volume 1 - Main Structure and Greater Capital City Statistical Areas, July 2011 (cat. no. 1270.0.55.001).
Australian Standard Geographical Structure - Main Structure
27 The ABS Structures are a hierarchy of regions developed for the release of particular ABS statistics. Their components are described below:
28 For the purposes of this publication, Jervis Bay Territory, Christmas Island and Cocos (Keeling) Islands are collectively referred to as 'Other Territories' and are included in the totals for Australia.
29 For further information see Australian Statistical Geography Standard (ASGS): Volume 1 - Main Structure and Greater Capital City Statistical Areas, July 2011 (cat. no. 1270.0.55.001).
30 The purpose of the Remoteness Structure is to divide Australia into broad geographic regions that share common characteristics of remoteness for statistical purposes. The Remoteness Structure divides each state and territory into several regions on the basis of their relative access to services. Remoteness Areas (RAs) are the spatial units that make up the ASGS Remoteness Structure. There are six classes of RA in the Remoteness Structure: Major Cities of Australia, Inner Regional Australia, Outer Regional Australia, Remote Australia, Very Remote Australia and Migratory.
31 Within each state/territory, each RA represents an aggregation of non-contiguous geographical areas which share common characteristics of remoteness (constructed from SA1s). 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 Statistical Geography Standard (ASGS): Volume 5 - Remoteness Structure, July 2011 (cat. no. 1270.0.55.005).
Indigenous Geography Structure
33 Data are also presented according to the Indigenous Structure of the Australian Statistical Geography Standard (ASGS). Under this classification, areas are defined as follows:
34 For further information see Australian Statistical Geography Standard (ASGS): Volume 2 - Indigenous Structure, July 2011 (cat. no. 1270.0.55.002).
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 suppressed.
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 Rest of Victoria. In Tasmania, Remote Australia, and Very Remote Australia have been combined to produce Rest 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 publication 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.
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