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7 The 2011 Census of Population and Housing (Household Form) asked the following question of each person:
Australian statistical areas
8 This release contains data presented according to a number of geographic classifications: the Main Structure of the Australian Statistical Geography Standard (ASGS), the Indigenous Structure, and Remoteness Areas (RAs).
9 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); Australian Statistical Geography Standard (ASGS): Volume 2 - Indigenous Structure, July 2011 (cat. no. 1270.0.55.002); and Australian Statistical Geography Standard (ASGS): Volume 5 - Remoteness Structure, July 2011 (cat. no. 1270.0.55.005).
10 Estimates and projections in this release are presented by five-year age groups, with upper age groups as follows:
11 Single year of age data is available on request for Australia and the states and territories, excluding the Australian Capital Territory and Other Territories. Single year of age data for these jurisdictions is not available (see paragraphs 34-35).
12 It is important to recognise the inherent uncertainties in these data. Aboriginal and Torres Strait Islander population estimates for 30 June 2011, on which the estimates and projections in this release are based, may be subject to errors that cannot be adjusted for in the population estimates compilation process. This is due to the inability of the Post Enumeration Survey to adjust for net undercount by Indigenous status by single year of age and sex. For example, features present in single year of age Census counts, such as age heaping, will most likely appear in population estimates for 2011, even after adjustment for net undercount and other factors, and therefore may appear in single year of age estimates for earlier years as well as projections.
13 An age heaping adjustment has been applied to the population of the Northern Territory at 30 June 2011. This information was released in Estimates of Aboriginal and Torres Strait Islander Australians, June 2011 (cat. no. 3238.0.55.001) and has been used as the base population for the estimates and projections in this release.
14 In addition, the use of assumptions on future levels of fertility, mortality and migration to obtain population projections adds a further level of uncertainty, the extent of which cannot be measured.
15 There are many techniques which may be used to produce population projections, such as simple extrapolations, probabilistic methods, broad economic, social and time-series analysis, and detailed component methods.
16 As mentioned above (see paragraphs 3-5), data quality issues relating to Census counts, births, deaths and migration of Aboriginal and Torres Strait Islander persons do not support the standard approach to population estimation. An alternative method is therefore required to enable the construction of a time series of the size and structure of the Aboriginal and Torres Strait Islander population.
17 Estimates of the Aboriginal and Torres Strait Islander population are available for 30 June of the latest Census year (currently, 30 June 2011). Based on these, estimates (for previous years) and projections (for future years) can be derived using assumptions about past and future components of population change.
18 Due to volatility in Aboriginal and Torres Strait Islander Census counts, estimates for previous years derived from the 30 June 2011 data provide a consistent time series compared to Census year estimates derived from previous censuses. The estimates and projections in this release therefore supersede previously published ABS estimates and projections of the Aboriginal and Torres Strait Islander population. See paragraphs 31-33 for a comparison of population estimates based on the 2006, 2001 and 1996 censuses.
19 The ABS uses the cohort-component method, which begins with a base population for each sex by single year of age, and advances it year by year by applying assumptions regarding future fertility, mortality and migration. This procedure is repeated for each year in the projection period. Projections for each geographic region (for example, Remoteness Areas) by sex and single years of age are adjusted to sum to state or territory projections which are in turn adjusted to sum to Australia-level projections.
20 A similar technique can also be used to estimate past populations, by 'reverse-surviving' a population using mortality rates derived from life tables.
21 A single series of population estimates for the period 1996 to 2010 was calculated by reverse-surviving the 30 June 2011 estimated Aboriginal and Torres Strait Islander resident population using assumed life tables based on those calculated for the period 2010-2012. Zero net overseas migration was assumed for the period 1996 to 2011 and interstate migration levels were based on those measured in the corresponding intercensal period (i.e. 1996-2001, 2001-2006 and 2006-2011).
Method used to derive estimates
22 Using 30 June 2011 Aboriginal and Torres Strait Islander resident population estimates as the base population, estimates were survived back one year at a time to 30 June 1996. For example, the number of 19-year old males in 2010 was obtained by applying survivorship ratios from life tables to the number of 20-year old males in 2011. This calculation is performed for all ages and both sexes to obtain the complete 2010 population, and repeated to obtain estimates for each year back to 1996.
23 Net interstate migration assumptions have been calculated directly from the net migration measured in the corresponding Census periods. As Census data indicates that the level of net overseas migration of Aboriginal and Torres Strait Islander persons is negligible, zero net overseas migration has been assumed.
24 For the estimates presented in this release, it was assumed that Aboriginal and Torres Strait Islander life expectancy at birth at the Australia level increased by 0.2 years per year for males and 0.15 years per year for females for the period 30 June 1996 to 30 June 2006 and then increased by 0.3 years per year for males and 0.15 years per year for females for the 2006-2011 period. Under this assumption, life expectancy at birth in 1996 would be 65.5 years and 71.4 years for Aboriginal and Torres Strait Islander males and females respectively. Whether Aboriginal and Torres Strait Islander life expectancy at birth has changed at a faster or slower rate is unknown.
Comparison to previously published estimates
25 The estimate for 30 June 2006 based on the 2006 Census was 517,000 Aboriginal and Torres Strait Islander persons. The estimate for 2006 presented in this release, based on the 2011 Census, is 601,500 persons (16% more than the previously published 2006 estimate).
26 The total Aboriginal and Torres Strait Islander population of Australia at 30 June 2001, based on the 2001 Census, was 458,500 persons. The estimate for 2001 presented in this release, based on the 2011 Census, is 534,700 persons (17% more than the previously published 2001 estimate).
27 The estimate for 30 June 1996 based on the 1996 Census was 386,000 persons. The estimate for 1996 presented in this release, based on the 2011 Census, is 468,200 persons (21% more than the previously published 1996 estimate).
28 The ABS publishes Aboriginal and Torres Strait Islander population projections once every intercensal period. The projections are not intended as predictions or forecasts, but are illustrations of growth and change in the structure of the Aboriginal and Torres Strait Islander population that would occur if assumptions made about future demographic trends were to prevail over the projection period.
29 Assumptions have been formulated on the basis of past demographic trends, in conjunction with consultation with various experts and government department representatives at the national and state/territory level. Consultation occurred between November 2013 and February 2014, after which the assumptions were finalised.
30 The assumptions do not attempt to allow for non-demographic factors (such as major government policy decisions, economic factors, natural disasters, epidemics or significant health treatment improvements) which may affect future demographic behaviour or outcomes. There is no certainty that any of the assumptions will or will not be realised. For detailed information on the assumptions used, see Chapter 2 for more information.
31 Projections incorporating alternative levels and combinations of assumptions have been produced in recognition of this uncertainty and to provide a range of possible options to users (see Chapter 4 for more information).
Method used to derive projections
32 Using 30 June 2011 Aboriginal and Torres Strait Islander resident population estimates as the base population, the estimates were projected forward one year at a time to 30 June 2026. For example:
33 The result of these steps is the projected population for 2012. This process is repeated to produce each successive year of the projection, until the year 2026.
34 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 and make assurances that any statistical information about individual respondents cannot be derived from published data.
35 Some techniques used to guard against identification or disclosure of confidential information in statistical tables are suppression of sensitive cells, random adjustments to cells with very small values, and aggregation of data. To protect confidentiality within this release, some cell values may have been suppressed and are not available for release but included in totals where applicable. In these cases data may not sum to totals due to the confidentialisation of individual cells.
36 In this release population estimates and projections, and their components have sometimes been rounded. Rounded figures and unrounded figures should not be assumed to be accurate to the last digit shown. Where figures have been rounded, discrepancies may occur between sums of component items and totals.
37 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 PUBLICATIONS AND REFERENCES
38 Other ABS publications that may be of interest to users include:
Australian Demographic Statistics (cat. no. 3101.0)
Births, Australia (cat. no. 3301.0)
Census of Population and Housing: Understanding the Increase in Aboriginal and Torres Strait Islander Counts, 2006-2011 (cat. no. 2077.0)
Deaths, Australia (cat. no. 3302.0)
Demography Working Paper 2001/4 - Issues in Estimating the Aboriginal and Torres Strait Islander Population (cat. no. 3126.0)
Discussion Paper: Assessment of Methods for Developing Life Tables for Aboriginal and Torres Strait Islander Australians, Australia, 2006 (cat. no. 3302.0.55.002)
Estimates of Aboriginal and Torres Strait Islander Australians, June 2011 (cat. no. 3238.0.55.001)
Experimental Estimates and Projections, Aboriginal and Torres Strait Islander Australians, 1991 to 2021 (cat. no. 3238.0)
Life Tables for Aboriginal and Torres Strait Islander Australians, 2010-2012 (cat. no. 3302.0.55.003)
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 (cat. no. 4704.0)
ADDITIONAL STATISTICS AVAILABLE
39 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.
40 ABS products and publications are available free of charge from the ABS web site <https://www.abs.gov.au>. Click on Statistics to gain access to the full range of ABS statistical and reference information.
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