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3238.0 - Experimental Estimates and Projections, Aboriginal and Torres Strait Islander Australians, 1991 to 2021 Quality Declaration 
Previous ISSUE Released at 11:30 AM (CANBERRA TIME) 08/09/2009   
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EXPLANATORY NOTES


INTRODUCTION

1 This publication contains experimental estimates of the Aboriginal and Torres Strait Islander (Indigenous) population of Australia from 30 June 1986 to 30 June 2006, and projections of the Indigenous population from 30 June 2007 to 30 June 2021, based on results of the 2006 Census of Population and Housing.

2 Due to the inherent uncertainties in these data, the estimates and projections presented in this publication are referred to as experimental. Caution should be exercised when interpreting them.

3 These estimates and projections supercede the 2001-based series published in Experimental Estimates and Projections, Aboriginal and Torres Strait Islander Australians, 1991 to 2009 (cat. no. 3238.0) in September 2004.


DATA QUALITY

4 The significant volatility in Indigenous census counts and the quality of data on births, deaths and migration of Indigenous persons do not support the use of the standard approach to population estimation, in which observed numbers of births, deaths and migration during a specified period are added to the population at the start of the period to obtain an estimate of the population at the end of the period.

5 Data quality issues relating to Indigenous population estimates for 30 June 2006 derived from the 2006 Census of Population and Housing, on which the estimates and projections in this publication are based, are discussed in more detail in paragraphs 9 to 22 of the Explanatory Notes of Experimental Estimates of Aboriginal and Torres Strait Islander Australians, Jun 2006 (cat. no. 3238.0.55.001) and the associated Technical Note: Estimated Aboriginal and Torres Strait Islander Australian Resident Population - Method of Calculation.

6 For a discussion of the measurement of deaths of Indigenous persons, see Chapter 2 of Experimental Life Tables for Aboriginal and Torres Strait Islander Australians, 2005-2007 (cat. no. 3302.0.55.003).


CLASSIFICATIONS

Indigenous status

7 The Indigenous population 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.

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

Diagram: 6.14 Indigenous status


Australian statistical areas

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

Australian Standard Geographical Classification - Main Structure

10 The Australian Standard Geographical Classification (ASGC) is a hierarchical classification system consisting of six interrelated classification structures. The ASGC provides a common framework of statistical geography and thereby enables the production of statistics which are comparable and can be spatially integrated.

11 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.

12 Population estimates and projections have been produced separately for each state and territory of Australia, excluding Jervis Bay Territory, Christmas Island and Cocos (Keeling) Islands. These three regions, collectively referred to as 'Other Territories' (OT), have been combined and included in totals for Australia.

13 Estimates and projections are not available for other geographies within the ASGC.

14 For further information refer to Australian Standard Geographical Classification (ASGC) (cat. no. 1216.0).

Australian Indigenous Geographical Classification

15 Population projections are also presented according to the Australian Indigenous Geographical Classification (AIGC) which refers to boundaries as defined at 1 July 2006. Under this classification, population projections were produced for:
  • 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.

16 Projections are not available for lower level geographies within the AIGC.

17 For further information refer to Maps and Census Profiles, Australian Indigenous Geographical Classification, 2006 (cat. no. 4706.0.30.001).

Remoteness Areas

18 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. Under this classification, Indigenous population projections were produced for:
  • Major Cities of Australia;
  • Inner Regional Australia and Outer Regional Australia combined; and
  • Remote Australia and Very Remote Australia combined.

19 Projections are not available for lower level geographies within the Remoteness Areas classification.

20 For further information refer to Australian Standard Geographical Classification (ASGC) (cat. no. 1216.0).


Age groups

21 Estimates and projections in this publication are presented by 5-year age groups, with upper age groups as follows:
  • Australia, states and territories - 85 years and over (65 years and over for Tasmania and the Australian Capital Territory);
  • Indigenous Regions - 65 years and over; and
  • Remoteness Areas - 75 years and over.

22 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 45-46).

23 It is important to recognise the inherent uncertainties in these data. Indigenous population estimates for 30 June 2006, on which the estimates and projections 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 2006, 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.

24 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.


METHODS

25 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.

26 As mentioned above, data quality issues relating to census counts, births, deaths and migration of Indigenous 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 Indigenous population.

27 Estimates of the Indigenous population are available for 30 June of the latest census year (currently, 30 June 2006). 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.

28 Due to volatility in Indigenous census counts, estimates for previous years derived from the 30 June 2006 data provide a consistent time series compared to census year estimates derived from previous censuses. The estimates in this publication therefore supercede previously published ABS estimates and projections of the Indigenous population. See paragraphs 36-38 for a comparison of population estimates based on the 2006, 2001 and 1996 censuses.


Cohort-component method

29 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, Indigenous Regions) 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.

30 A similar technique can also be used to estimate past populations, by 'reverse-surviving' a population using mortality rates derived from life tables.


ESTIMATES

31 A single series of population estimates for the period 1986 to 2005 was calculated by reverse-surviving the 30 June 2006 experimental estimated Indigenous resident population using assumed life tables based on those calculated for the period 2005-2007. Zero net interstate and overseas migration was assumed for the period 1986 to 2006.


Method used to derive estimates

32 Using 30 June 2006 experimental Indigenous resident population estimates as the base population, estimates were survived back one year at a time to 30 June 1986. For example, the number of 19-year old males in 2005 was obtained by applying survivorship ratios from life tables to the number of 20-year old males in 2006. This calculation is performed for all ages and both sexes to obtain the complete 2005 population, and repeated to obtain estimates to 1986.

33 The absolute size of net interstate migration does not warrant a specific assumption in constructing these estimates. As such, zero internal migration has been assumed. As census data indicates that the level of net overseas migration of Indigenous persons is negligible, zero net overseas migration has been assumed.

34 For the 2001-based Indigenous population estimates a constant life expectancy at birth assumption was assumed. However, it is unlikely that life expectancy at birth for Indigenous Australians has remained unchanged over the past 15 years at 2005-2007 levels. For the estimates presented in this publication, it was assumed that Indigenous life expectancy at birth at the Australia level increased by 0.2 years per year for the period 30 June 1986 to 30 June 2006 for both males and females. Under this assumption, life expectancy at birth would be 64.1 years for Indigenous males and 69.8 years for Indigenous females in 1991. Whether Indigenous life expectancy at birth has changed at a faster or slower rate is unknown.


Estimates for 1986 to 1990

35 Given the 20-year interval for which the assumption of improving life expectancy at birth is applied, as well as the assumption of zero net interstate migration over the period, estimates for 1986 to 1990 should be interpreted with caution.


Comparison to previously published estimates

36 The total Indigenous population of Australia at 30 June 2001, based on the 2001 Census, was 458,500 persons. The estimate for 2001 presented in this publication, based on the 2006 Census, is 463,100 persons (1% greater than the previously published 2001 estimate).

37 The estimate for 30 June 1996 based on the 1996 Census was 386,000 persons. The estimate for 1996 presented in this publication, based on the 2006 Census, is 407,300 persons (5.5% greater than the previously published 1996 estimate).

38 The estimate for 30 June 1991 based on the 1991 Census was 283,000 persons. The estimate for 1991 presented in this publication, based on the 2006 Census, is 351,000 persons (24% greater than the previously published 1991 estimate).


PROJECTIONS

39 The ABS publishes Indigenous population projections once every intercensal period. The projections are not intended as predictions or forecasts, but are illustrations of growth and change in the Indigenous population that would occur if assumptions made about future demographic trends were to prevail over the projection period.


Assumptions

40 Assumptions have been formulated on the basis of past demographic trends, in conjunction with consultation with various individuals and government department representatives at the national and state/territory level. Consultation occurred between May and July 2009, after which the assumptions were finalised.

41 The assumptions do not attempt to allow for non-demographic factors (such as major government policy decisions, economic factors, catastrophes, wars, 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.

42 Projections incorporating alternative levels and combinations of assumptions have been produced in recognition of this uncertainty and to provide a range of options to users (see Chapter 4 for more information).


Method used to derive projections

43 Using 30 June 2006 experimental Indigenous resident population estimates as the base population, the estimates were projected forward one year at a time to 30 June 2021. For example:
  • the number of 21-year old males in 2007 was obtained by applying survivorship ratios from life tables to the number of 20-year old males in 2006. This calculation is performed for all ages and both sexes to obtain a 'survived' population for 2007;
  • net interstate migration (by single year of age and sex) for 2007 was derived by applying migration rates to the 2006 Indigenous population and adding these to the relevant state or territory population; and
  • to obtain the number of 0-year olds in 2007, age-specific fertility and paternity rates were applied to the female and male populations (respectively) aged 15-49 years to derive the number of births (that is, 0-year olds). These are split into males and females using the assumed sex ratio at birth.

44 The result of these steps is the projected population for 2007. This process is repeated to produce each successive year of the projection, until the projection horizon is reached.


CONFIDENTIALITY

45 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.

46 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 publication, some cell values may have been suppressed and are not available for publication but included in totals where applicable. In these cases data may not sum to totals due to the confidentialisation of individual cells.


ROUNDING

47 In this publication 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.


ACKNOWLEDGEMENTS

48 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

49 Other ABS publications that may be of interest to users include:

ADDITIONAL STATISTICS AVAILABLE

50 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.

51 ABS products and publications are available free of charge from the ABS web site <http://www.abs.gov.au>. Click on Statistics to gain access to the full range of ABS statistical and reference information.


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