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4713.0 - Population characteristics, Aboriginal and Torres Strait Islanders Australians, 2001  
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Feature Article - Estimated Resident Indigenous Population-method of calculation.


ESTIMATED RESIDENT INDIGENOUS POPULATION


METHOD OF CALCULATION


This article originally appeared as appendix 1 in ABS publication Population Characteristics, Aboriginal and Torres Strait Islander Australians, 2001 (ABS cat. no. 4713.0)

Adjustments

Experimental estimates of the resident Indigenous population are based on 2001 Census usual residence counts and make allowance for instances in which Indigenous status is unknown, and for net underenumeration. The number of cases where Indigenous status was unknown in the 2001 Census and changed to 'Indigenous' for estimates of the resident Indigenous population is shown for States, Territories and Australia, in the table below.


IMPUTED INDIGENOUS STATUS(a)
Status unknown imputed to Indigenous
State/Territory
no.
New South Wales
5,052
Victoria
991
Queensland
4,762
South Australia
725
Western Australia
2,685
Tasmania
520
Northern Territory
1,567
Australian Capital Territory
134

Australia(b)
16,438

(a) Usual residence 2001 Census records with Indigenous status unknown.
(b) Includes Other Territories.


The process for estimating the population as at 30 June also involves an adjustment from 7 August 2001 back to 30 June 2001 for natural increase.

Estimates are considered experimental in that the standard approach to population estimation is not possible because satisfactory data on births, deaths and migration are not generally available, and because of the intercensal volatility in Census counts of the Indigenous population.

Projections of the resident Indigenous population based on 1996 Census data were published in 1998. Two series (a high series and a low series) were produced which were based on different assumptions about the extent of changes in the propensity to identify as Indigenous in the Census. Estimates of the resident Indigenous population based on 2001 Census data show that the observed population growth for the intercensal period occurred in the expected range.

Indigenous status unknown

It is assumed that some people for whom the Indigenous status question in the Census is not completed are actually of Indigenous origin. Some of the Census records for which Indigenous status is unknown were therefore categorised as Indigenous, according to the ratio of the Indigenous response to the total stated responses. This allocation was made separately for males and females by age groups and form type, for each Statistical Local Area (SLA). SLAs aggregate to form larger spatial units, such as Statistical Divisions, States/Territories, and Australia. Some estimates were adjusted on the basis of specific information.

Census net undercount

While every effort is made to ensure full coverage of people and dwellings in the Census, inevitably small numbers of people will have been missed while others will have been counted more than once. In Australia more people are missed from the Census than are counted more than once. The net effect of overcount and undercount is called net undercount.

To measure net undercount of the Australian population in the Census the ABS conducts a Post Enumeration Survey (PES) shortly after the Census. The PES is a sample survey that aims to provide an independent check of the Census coverage. The survey uses a sample of two-thirds of 1% of private dwellings in Australia. In PES processing, the information collected in the PES is matched against corresponding Census forms for those same dwellings to determine whether a person has been counted more than once or not counted at all. The resulting measure of net undercount is applied to Census usual residence counts in deriving population estimates.

Reliability of PES estimates

Since the PES estimates are based on information obtained from occupants of a sample of dwellings, they are subject to sampling variability; that is, they may differ from the figures that would have been produced if all dwellings had been included.

One measure of the likely difference is given by the standard error (SE), which indicates the extent to which estimates might have varied by chance because only a sample of dwellings was included. The SE for the estimate of the net undercount for the total Australian population on a usual residence basis (1.8%) is 0.1. The SE for the estimate of the net undercount for the total Indigenous population on a usual residence basis (6.1%) is 1.1.

Given an estimate and the SE on that estimate, there are about two chances in three that the sample estimate will differ by less than one SE from the figure that would have been obtained if all dwellings had been included, and about nineteen chances in twenty that the difference will be less than two SEs.

The following example illustrates the use of the concept of SE.

    If an estimate of 6.1% has a SE of 1.1 percentage points there are two chances in three that the figure that would have been obtained if all dwellings had been included in the sample is in the range 6.1% (1 x 1.1%) or 5.0% to 7.2% and nineteen chances in twenty that the figure would have been in the range 6.1% (2 x 1.1%) or 3.9% to 8.3%.

Indigenous undercount

All PES respondents were asked to report the Indigenous status of persons in their household. Although the PES sample was not designed specifically to include Aboriginal and Torres Strait Islander peoples, it included a small sample of Indigenous residents in private dwellings in non-sparsely settled areas. The Indigenous net undercount rate of about 6.1% was applied to all geographic areas in deriving the Indigenous population estimates. No separate undercount rate is derived for sparsely settled areas.

Using estimates and census characteristics data

When using Census counts broken down by person characteristics, for example labour force status and educational attainment, users should be aware that the data cannot be reconciled with population estimates because they represent Census counts which are not adjusted for underenumeration or the other factors discussed above. The only Census variables which are adjusted in population estimates are age, sex, place of usual residence, and Indigenous status, and the adjusted data are only available in the form of population estimates. Users should be careful when using Census characteristics data and estimates of the resident Indigenous population together.

FURTHER INFORMATION


For further information on estimated Indigenous resident population see Experimental Estimates of the Aboriginal and Torres Strait Islander Population, 30 June 1991 - 30 June 1996 (ABS cat. no. 3230.0) and Experimental Projections of the Aboriginal and Torres Strait Islander Population, 30 June 1996 to 30 June 2006 (ABS cat. no. 3231.0).


For further information and statistics on Indigenous Australians see:
Population Distribution, Aboriginal and Torres Strait Islander Population, 2001 (ABS cat. no. 4705.0)
Population Characteristics, Aboriginal and Torres Strait Islander Australians, 2001 (ABS cat. no. 4713.0)
The Health and Welfare of Australia's Aboriginal and Torres Strait Islander Peoples, 2003 (ABS cat. no. 4704).
More information on Indigenous statistics can be found on Indigenous theme page.

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