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2077.0 - Census of Population and Housing: Understanding the Increase in Aboriginal and Torres Strait Islander Counts, 2006-2011 Quality Declaration 
Latest ISSUE Released at 11:30 AM (CANBERRA TIME) 17/09/2013  First Issue
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MEASURING CHANGES IN POPULATION BETWEEN CENSUSES

INTRODUCTION

When an unexpectedly large increase is observed in the count of Aboriginal and Torres Strait Islander people between Censuses, such as that observed between the 1991 and 1996 Censuses (33%) and between the 2006 and 2011 Censuses (21%), some of the increase can be explained through demographic factors of population change such as births, deaths and migration. These are the components of change that can be measured using information collected in the Census of Population and Housing and in administrative datasets.

This chapter explores the demographic factors which account for part of the increase in counts of Aboriginal and Torres Strait Islander people between the 2006 and 2011 Censuses.

Note that Census data is not adjusted for undercount and so relates to Census counts, not population estimates. For this reason, the analysis in this chapter is repeated using population estimates in Technical Note 1: Measuring Change in Population Estimates of Aboriginal and Torres Strait Islander Peoples.


SUMMARY OF FINDINGS

  • Over two-thirds (65,500) of the 93,300 increase in the Census count of Aboriginal and Torres Strait Islander people between 2006 and 2011 can be accounted for by demographic factors of population change (that is, births, deaths and overseas migration).
  • The remaining one-third (27,800) of the increase that cannot be explained by demographic factors equates to 5% of the total 2011 Census count of Aboriginal and Torres Strait Islander people.

FRAMEWORK FOR MEASURING CHANGE

In order to measure the change in Census counts between 2006 and 2011, the net effects of births, deaths and overseas migration are added (or subtracted) to the 2006 Census count of Aboriginal and Torres Strait islander people to produce an expected 2011 count. If it were possible to achieve complete coverage in Census enumeration, and consistency in the reporting and recording of each person's Indigenous status, change in Census counts between the 2006 and 2011 Censuses would be entirely attributable to births, deaths and migration combined - that is, the expected count for 2011 would match the actual Census count of Aboriginal and Torres Strait Islander people in 2011. In reality there will always be an element of the total change in counts between Censuses that cannot be explained, such as the change that occurs as a result of individuals identifying as an Aboriginal and/or Torres Strait Islander person in one Census but not in another, as well as errors in the measurement of births, deaths and migration. This can be represented as:

    Census count 1
      + births registered between Census 1 and Census 2
      - deaths registered between Census 1 and Census 2
      +/- net migration between Census 1 and Census 2
      +/- the impact of factors which cannot be explained by measurable components of population change
    = Census count 2


Despite the best efforts of the Australian Bureau of Statistics (ABS) to collect a complete set of information from all people in Australia on Census night, there will always be some people for whom Indigenous status is not reported. In the 2011 Census, there were 1,058,600 records where Indigenous status was unknown. While some people with an unknown Indigenous status will be of Aboriginal and/or Torres Strait Islander origin and some will be non-Indigenous people, the exact proportions cannot be determined from Census data. This complicates analysis of Census counts, given that missing Indigenous status is not imputed in the Census, but is instead imputed following the Post Enumeration Survey for use in producing population estimates. For this reason, the analysis presented in this chapter is based on the 548,400 people who identified as being of Aboriginal and/or Torres Strait islander origin in 2011.


COMPONENTS OF CHANGE IN CENSUS COUNTS OF ABORIGINAL AND TORRES STRAIT ISLANDER PEOPLES

Births and deaths

Birth and death registrations are important components of many demographic estimates, such as population estimates and calculations of life expectancy at birth. The ABS and the state and territory Registrars of Births, Deaths and Marriages are committed to improving the identification of Aboriginal and Torres Strait Islander people and also the completeness and accuracy of the recording of Indigenous status on birth and death registration forms. However, some Aboriginal and Torres Strait Islander people are not correctly identified or recorded as such when their birth or death is registered.

It is generally assumed that the number of registered births and deaths understates the level of fertility and mortality in the Aboriginal and Torres Strait Islander population and so projected births would normally be used in this analysis, given they take into account this under-identification. However, between 2006 and 2011, the number of registered births exceeded the number of projected births in some jurisdictions. This increase in births registrations is consistent with the increase in the Census count of Aboriginal and Torres Strait Islander people. For this reason, births and deaths registrations rather than projections have been used.

At the national level, over two-thirds (69%) of the increase in Census counts of Aboriginal and Torres Strait Islander people between 2006 and 2011 can be attributed to natural increase (births minus deaths). The combined contribution of births (increase) and deaths (decrease) explains more of the overall increase in counts of Aboriginal and Torres Strait Islander people in some jurisdictions than in others. In the Australian Capital Territory, just under half (47%) of the overall increase can be attributed to natural increase, while in Western Australia natural increase accounted for most (85%) of the increase. In contrast, natural increase was greater than the overall increase in Census counts for Aboriginal and Torres Strait Islander people in the Northern Territory, with other factors, such as interstate migration, having contributed an offsetting effect.


CHANGE DUE TO BIRTHS AND DEATHS, Aboriginal and Torres Strait Islander people(a), 2006-2011

Census count
Relative change
Births(b)
Deaths(b)
Change due to
births and deaths(c)
2006
2011
2006-2011
2006-2011
2006-2011
2006-2011
no.
no.
no.
%
no.
no.
no.
%

New South Wales
138 506
172 622
34 116
24.6
21 015
2 959
18 056
52.9
Victoria
30 143
37 991
7 848
26.0
5 183
554
4 629
59.0
Queensland
127 580
155 826
28 246
22.1
23 673
3 313
20 360
72.1
South Australia
25 556
30 433
4 877
19.1
4 449
717
3 732
76.5
Western Australia
58 710
69 666
10 956
18.7
11 570
2 214
9 356
85.4
Tasmania
16 768
19 627
2 859
17.1
1 949
139
1 810
63.3
Northern Territory
53 663
56 777
3 114
5.8
7 846
2 264
5 582
179.3
Australian Capital Territory
3 873
5 185
1 312
33.9
673
55
618
47.1
Australia
455 028
548 370
93 342
20.5
76 378
12 218
64 160
68.7

(a) Usual residence Census counts. Excludes overseas visitors. Includes Other Territories.
(b) Registered births and deaths.
(c) Registered births minus registered deaths.
Note: Totals and components may not be consistent within and between tables due to introduced random error to protect confidentiality of Census respondents - see Census Dictionary, 2011 (cat. no. 2901.0).


Overseas migration

Information on overseas migration is collected in the Census, in response to the question "What was your place of usual residence five years ago?". People who answer this question by stating they were overseas are assumed to have migrated to Australia after the last Census and before the current Census.

Overseas migration figures from the Census show that Aboriginal and Torres Strait Islander people who migrated to, or returned to, Australia between 2006 and 2011 accounted for 1.5% (1,400) of the increase in Census counts of Aboriginal and Torres Strait Islander people during this period.

Other sources of overseas migration such as arrival and departure cards do not collect the Indigenous status of individuals and as such cannot be used as an accurate source of the overseas migration of Aboriginal and Torres Strait Islander people.

Interstate migration

Within Australia, migration between the states and territories provides important insight into population changes at the jurisdictional level. Information on internal migration is collected in the Census, in response to the question "What was your place of usual residence five years ago?".

Queensland, Victoria, South Australia, Western Australia and the Australian Capital Territory recorded a net gain in Aboriginal and Torres Strait Islander residents from interstate migration between 2006 and 2011, meaning the counts of Aboriginal and Torres Strait Islander people who moved into those jurisdictions was higher than the counts of Aboriginal and Torres Strait Islander people who moved out of them. Over the same period, New South Wales, the Northern Territory and Tasmania experienced net loss from interstate migration. Although the net loss was highest in New South Wales (2,000 Aboriginal and Torres Strait Islander people), as a proportion of the change in Census counts it was highest in the Northern Territory (26%). This net loss equates to 1.5% of the Census count of Aboriginal and Torres Strait Islander people in the Northern Territory in 2006.

Data on interstate migration are not adjusted for Census undercount so it is likely these figures underestimate the number of 'movers in' and 'movers out' for all states and territories to varying degrees.


CHANGE DUE TO INTERSTATE MIGRATION, Aboriginal and Torres Strait Islander people(a), 2006-2011

Census count
Relative change
Movers in
(b)
Movers out(c)
Change due to
interstate migration (d)
2006
2011
2006-2011
2006-2011
2006-2011
2006-2011

no.
no.
no.
%
no.
no.
no.
%

New South Wales
138 506
172 622
34 116
24.6
4 592
6 588
-1 996
-5.9
Victoria
30 143
37 991
7 848
26.0
2 892
2 059
833
10.6
Queensland
127 580
155 826
28 246
22.1
6 434
5 222
1 212
4.3
South Australia
25 556
30 433
4 877
19.1
1 616
1 290
326
6.7
Western Australia
58 710
69 666
10 956
18.7
2 235
1 941
294
2.7
Tasmania
16 768
19 627
2 859
17.1
777
828
-51
-1.8
Northern Territory
53 663
56 777
3 114
5.8
1 831
2 624
-793
-25.5
Australian Capital Territory
3 873
5 185
1 312
33.9
932
782
150
11.4
Australia
455 028
548 370
93 342
20.5
. .
. .
. .
0.0

(a) Usual residence Census counts. Excludes overseas visitors. Includes Other Territories.
(b) People who migrated into that state/territory from another state/territory.
(c) People who migrated out of that state/territory to another state/territory.
(d) Movers in minus movers out.
Note: Totals and components may not be consistent within and between tables due to introduced random error to protect confidentiality of Census respondents - see Census Dictionary, 2011 (cat. no. 2901.0).


ERROR OF CLOSURE - CENSUS COUNTS OF ABORIGINAL AND TORRES STRAIT ISLANDER PEOPLES

Over two-thirds (65,500) of the 93,300 person increase in Census counts of Aboriginal and Torres Strait Islander people between 2006 and 2011 can be accounted for by births, deaths and overseas migration. This leaves just over one-third (27,800) of the increase in the count of Aboriginal and Torres Strait Islander people in 2011 that cannot be explained by the standard demographic components of population change. This unexplained component of the Census increase is referred to as the 'error of closure'.

'Error of closure' is a demographic term for the difference between the observed Census count and the expected Census count based on the previous count and changes due to demographic factors during the period between the Censuses. The term 'error of closure' does not imply a mistake, imprecision, or data quality issues, but is a term commonly used by demographers to denote differences between two population counts that cannot be explained by the demographic factors of population change.

The error of closure represents population change that may be explained by factors such as changing fertility rates, patterns of inter-partnering, and changes in the propensity of people to identify as being of Aboriginal and/or Torres Strait Islander origin between Censuses. These factors are explored in Changing Propensity to Identify as Being of Aboriginal and Torres Strait Islander Origin between Censuses. The error of closure is expressed as a percentage of the 2011 Census count, and represents 5% of the total 2011 Census count for Aboriginal and Torres Strait Islander people.

The error of closure rate varied by state and territory, with rates higher than the national rate observed in the Australian Capital Territory (10%), New South Wales (10%) and Victoria (6%).


ERROR OF CLOSURE IN CENSUS COUNTS, Aboriginal and Torres Strait Islander people(a), 2006-2011

Census count
Relative change
Measurable change 2006-2011
Error of closure(b)
2006
2011
2006-2011
Natural increase(c)
Overseas migration
Interstate migration
Total
no.
no.
no.
%
no.
no.
no.
no.
%
no.
%(d)

New South Wales
138 506
172 622
34 116
24.6
18 056
411
-1 996
16 471
48.3
17 645
10.2
Victoria
30 143
37 991
7 848
26.0
4 629
174
833
5 636
71.8
2 212
5.8
Queensland
127 580
155 826
28 246
22.1
20 360
435
1 212
22 007
77.9
6 239
4.0
South Australia
25 556
30 433
4 877
19.1
3 732
57
326
4 115
84.4
762
2.5
Western Australia
58 710
69 666
10 956
18.7
9 356
172
294
9 822
89.6
1 134
1.6
Tasmania
16 768
19 627
2 859
17.1
1 810
37
- 51
1 796
62.8
1 063
5.4
Northern Territory
53 663
56 777
3 114
5.8
5 582
44
-793
4 833
155.2
-1 719
-3.0
Australian Capital Territory
3 873
5 185
1 312
33.9
618
45
150
813
62.0
499
9.6
Australia
455 028
548 370
93 342
20.5
64 160
1 375
. .
65 535
70.2
27 807
5.1

(a) Usual residence Census counts. Excludes overseas visitors. Includes Other Territories.
(b) Total population change minus total measurable change.
(c) Registered births minus registered deaths.
(d) Proportion of the total count for each jurisdiction.
Note: Totals and components may not be consistent within and between tables due to introduced random error to protect confidentiality of Census respondents - see Census Dictionary, 2011 (cat. no. 2901.0).


The 3,100 increase in the Census count of Aboriginal and Torres Strait Islander people in the Northern Territory between 2006 and 2011 was lower than expected. The increase attributable to natural increase in the Northern Territory (5,600) was considerably higher than the overall increase in its Census count. This indicates that some parents may have identified their children as being of Aboriginal and/or Torres Strait Islander origin in birth registrations but not in the 2011 Census, or have moved interstate after their child's birth was registered. It may also mean that some Aboriginal and/or Torres Strait Islander people who have moved out of the Northern Territory since 2006 have not recorded their previous address in the 2011 Census.

The Northern Territory also recorded an increase between 2006 and 2011 in the number of returned Census forms with no response to the Indigenous status question, while the number of ‘not stated’ responses decreased in all other states and the territories. It is reasonable to assume that some of these records were for people of Aboriginal and/or Torres Strait Islander people origin, so this increase in 'not stated' responses is considered to have contributed to the lower than expected increase in Census counts of Aboriginal and Torres Strait Islander people in the Northern Territory. For more information about people with an unknown Indigenous status in the Census, refer to Technical Note 2: People for Whom Indigenous Status is Unknown.


CENSUS ENUMERATION AND PROCESSING

Improvements in Census enumeration and processing are also potential contributors to change in Census counts, but these are factors which are not easily measured.

After each Census, there is an extensive review of procedures that results in improvements for the next Census. As a result of the evaluation following the 2006 Census, additional funding was provided to the ABS to improve the procedures specifically focused on counting Aboriginal and Torres Strait Islander people in the 2011 Census.

Operational improvements in the 2011 Census included an increase in staffing resources, a reduction in the size of Census collector workloads, and an increased focus on urban areas. To support these improvements there was an increased level of engagement with Aboriginal and Torres Strait Islander people prior to the 2011 Census. For more detailed information on the improvements to the procedures for counting Aboriginal and Torres Strait Islander people in the 2011 Census, refer to Information Paper: 2011 Census Special Enumeration Strategies (cat. no. 2911.0.55.004). While the impacts of operational changes are not easy to measure within Census data, these improved procedures were expected to result in higher data quality and better coverage of Aboriginal and Torres Strait Islander people in the 2011 Census.

During the processing of Census data, a series of edits are applied to remove inconsistencies and errors. In 2008, due to funding constraints, the ABS made the decision to leave Census editing procedures largely unchanged between the 2006 and 2011 Censuses. As a result, it is expected that any minor change in editing procedures between 2006 and 2011 has had little impact on the change in Aboriginal and Torres Strait Islander Census counts.

Indigenous Status not stated

In 2011, the number of Census records with an unknown Indigenous status was 1,058,600 (5% of the total count) compared with 1,133,400 (6% of the total count) in 2006. The difference of 74,800 records represents a 7% decrease in records with an unknown Indigenous status between the 2006 and 2011 Censuses. This means that more people had their Indigenous status recorded in 2011 than in 2006, and may account for some of the unexplained increase in Census counts of Aboriginal and Torres Strait Islander people between 2006 and 2011. For more information about people with an unknown Indigenous status in the Census, refer to Technical Note 2: People for Whom Indigenous Status is Unknown.


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