TECHNICAL NOTE 2 PEOPLE FOR WHOM INDIGENOUS STATUS IS UNKNOWN

PEOPLE FOR WHOM INDIGENOUS STATUS IS UNKNOWN

1 Despite the best efforts of the Australian Bureau of Statistics (ABS) to collect complete information from all people in Australia on Census night, there will always be a group of people for whom Indigenous status is not known. While some people with an unknown Indigenous status will be Aboriginal and/or Torres Strait Islander people, and some will be non-Indigenous people, the exact proportions cannot be determined from the Census data. This complicates analysis of Census counts, given Indigenous status is not imputed within Census information, but is instead imputed later within the Post Enumeration Survey for use in producing population estimates. (Imputation is a statistical process for predicting values where no response was provided to a question and a response could not be derived.)

2 The number of Census records with an unknown Indigenous status in the 2011 Census was 1,058,600 (5% of the total Census count) compared with 1,133,400 records (6% of the total Census 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 a known Indigenous status in 2011 than in 2006, and this may account for some of the 'unmeasurable' increase in Census counts of Aboriginal and Torres Strait Islander people between 2006 and 2011.

3 The Northern Territory had the highest proportion of records with an unknown Indigenous status in 2011 (8%), followed by Western Australia (6%) and Queensland and New South Wales (both 5%). Between the 2006 and 2011 Censuses, the proportion of records with an unknown Indigenous status fell in all states and territories, with the largest reductions observed in New South Wales (down 1.0 percentage point), followed by Tasmania (down 0.9 percentage points) and Victoria (down 0.8 percentage points).

	2006		2011			Change
	no.	%	no.	%		% points
New South Wales	391 274	6.0	342 923	5.0		-1.0
Victoria	266 028	5.4	246 893	4.6		-0.8
Queensland	224 909	5.8	224 206	5.2		-0.6
South Australia	69 318	4.6	62 934	3.9		-0.7
Western Australia	127 328	6.5	130 719	5.8		-0.7
Tasmania	22 903	4.8	19 380	3.9		-0.9
Northern Territory	16 505	8.6	17 391	8.2		-0.4
Australian Capital Territory	15 025	4.6	14 005	3.9		-0.7
Australia(c)	1 133 446	5.7	1 058 586	4.9		-0.8
(a) Usual residence Census counts. Excludes overseas visitors. (b) Proportions are based on total population for each state/territory. (c) Includes Other Territories. 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).

4 There are two broad situations which result in a person’s Indigenous status being unknown:

• the returned Census form does not have a response to the Indigenous status question (known as item non-response), or
• when no Census form is received from a dwelling the number of males and females and other key demographic variables are imputed. Indigenous status is not imputed for these records, but is coded to 'not stated'.

5 In non-private dwellings, a nominated person completes a summary Census form that lists all people staying there, and personal Census forms (which include the Indigenous status question) are distributed to each person on the summary form. If personal forms are not returned or not completed for all individuals listed on the summary form, the Indigenous status for these people is unknown. People in non-private dwellings accounted for 11% of people with an unknown Indigenous status in 2011. Nationally, people living in non-private dwellings were about three times more likely to have an unknown Indigenous status than people in private dwellings (16% compared with 5%). There was some variation by state and territory. For example, in the Australian Capital Territory, people living in non-private dwellings were about five times more likely to have an unknown Indigenous status than those living in private dwellings (17% compared with 3%) while in the Northern Territory people living in non-private dwellings were twice as likely to have an unknown Indigenous status than those living in private dwellings (16% compared with 8%).




INDIGENOUS STATUS UNKNOWN DUE TO IMPUTATION OF PERSONS

6 Imputation is a statistical process used to predict characteristics when individuals do not return a form, or no response is provided to a question and a response cannot be derived. Although Census records are imputed when the ABS does not obtain a Census form for residents of both private and non-private dwellings, most imputation occurs for non-response from residents in private dwellings. Key demographic variables (sex, age, place of usual residence and registered marital status) are imputed if no Census form is received.

7 Indigenous status is coded to 'not stated' for imputed records. In 2011, almost three-quarters (73% or 768,600) of records with an unknown Indigenous status were imputed records. Unknown Indigenous status due to imputation was highest for the Northern Territory (85% or 14,700) and lowest for Tasmania (62% or 11,900).

	Imputed records		Total unknown
	no.	%	no.
New South Wales	248 084	72.3	342 923
Victoria	169 388	68.6	246 893
Queensland	168 735	75.3	224 206
South Australia	41 525	66.0	62 934
Western Australia	103 237	79.0	130 719
Tasmania	11 929	61.6	19 380
Northern Territory	14 695	84.5	17 391
Australian Capital Territory	10 883	77.7	14 005
Australia(b)	768 561	72.6	1 058 586
(a) Usual residence Census counts. Excludes overseas visitors. (b) Includes Other Territories. 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).

8 The proportion of imputed records nationally decreased slightly between the 2006 and 2011 Censuses (from 4.1% in 2006 to 3.6% in 2011). The Northern Territory had the highest rate of imputation in 2011 (7%), followed by Western Australia (5%), while Tasmania had the lowest (2%). Western Australia, Queensland, and the Northern Territory all recorded an increase in the number of imputed records over this period.

	2006		2011		Change
	no.	%	no.	%	% points
New South Wales	280 805	4.3	248 084	3.6	-0.7
Victoria	179 743	3.6	169 388	3.2	-0.4
Queensland	165 161	4.2	168 735	3.9	-0.3
South Australia	44 538	2.9	41 525	2.6	-0.3
Western Australia	97 737	5.0	103 237	4.6	-0.4
Tasmania	13 523	2.8	11 929	2.4	-0.4
Northern Territory	14 059	7.3	14 695	6.9	-0.4
Australian Capital Territory	11 399	3.5	10 883	3.0	-0.5
Australia(d)	807 062	4.1	768 561	3.6	-0.5
(a) Usual residence Census counts. Excludes overseas visitors. (b) Excludes records where there was no response to the Indigenous status question. (c) Proportions are based on the total population for each state/territory. (d) Includes Other Territories.
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).

INDIGENOUS STATUS UNKNOWN DUE TO ITEM NON-RESPONSE

Geographic distribution

9 In 2011, about one-quarter (290,000 or 27%) of records with an unknown Indigenous status were due to item non-response. Unknown Indigenous status due to item non-response was highest for Tasmania (38% or 7,400) and South Australia (34% or 21,400) and lowest for the Northern Territory (16% or 2,700).

	Item non-response		Total unknown
	no.	%	no.
New South Wales	94 837	27.7	342 923
Victoria	77 508	31.4	246 893
Queensland	55 468	24.7	224 206
South Australia	21 408	34.0	62 934
Western Australia	27 484	21.0	130 719
Tasmania	7 448	38.4	19 380
Northern Territory	2 696	15.5	17 391
Australian Capital Territory	3 120	22.3	14 005
Australia(b)	290 022	27.4	1 058 586
(a) Usual residence Census counts. Excludes overseas visitors. (b) Includes Other Territories. 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).

10 The national item non-response rate for the Indigenous status question decreased from 1.7% in 2006 to 1.4% in 2011. All states and territories saw a decline in the proportion of item non-response, with Tasmania recording the largest decline (from 2.0% of the population in 2006 to 1.5% in 2011), followed by New South Wales, Victoria, South Australia and Western Australia (each down 0.4 percentage points).

	2006		2011			Change
	no.	%	no.	%		% points
New South Wales	110 469	1.8	94 837	1.4		-0.4
Victoria	86 285	1.8	77 508	1.4		-0.4
Queensland	59 748	1.6	55 468	1.3		-0.3
South Australia	24 780	1.7	21 408	1.3		-0.4
Western Australia	29 591	1.6	27 484	1.2		-0.4
Tasmania	9 380	2.0	7 448	1.5		-0.5
Northern Territory	2 446	1.4	2 696	1.3		-0.1
Australian Capital Territory	3 626	1.2	3 120	0.9		-0.3
Australia(d)	326 384	1.7	290 022	1.4		-0.4
(a) Usual residence Census counts. Excludes overseas visitors. (b) Excludes imputed records. (c) Proportions are based on total population for each state/territory. (d) Includes Other Territories.
Note: Totals and components may not be consistent within and between tables due to introduced random error to protect confidentiality of Census respondent - see Census Dictionary, 2011 (cat. no. 2901.0).

Age

11 In the 2011 Census, the rate of item non-response to the Indigenous status question was highest for people aged 75 years and over (4%), followed by those aged 65-74 years and those aged less than 15 years (both 2%).

	Aboriginal and Torres Strait Islander people	Non- Indigenous people	Total population	Item non-response
Age group (years)	no.	no.	no.	no.	%
0-4	67 417	1 282 737	1 373 623	23 469	1.7
5-14	129 670	2 463 907	2 639 370	45 793	1.7
15-24	105 654	2 615 638	2 755 468	34 176	1.2
25-34	71 804	2 733 687	2 830 762	25 271	0.9
35-44	67 674	2 852 517	2 946 432	26 241	0.9
45-54	53 148	2 765 169	2 846 356	28 039	1.0
55-64	32 231	2 358 925	2 419 984	28 828	1.2
65-74	14 174	1 534 486	1 578 416	29 756	1.9
75 and over	6 598	1 293 698	1 348 748	48 452	3.6
Australia(c)	548 370	19 900 764	20 739 159	290 022	1.4
(a) Usual residence Census counts. Excludes overseas visitors. (b) Excludes imputed records. (c) Includes Other Territories.
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).

Sex

12 Nationally, the rate of item non-response to the Indigenous status question was slightly higher for females (51%) than males (49%) in 2011. A similar trend was seen in most jurisdictions. In the Northern Territory, item non-response was greater for males than in any other jurisdiction (57% compared with 48% to 51% for all other states and the Australian Capital Territory). However, this is because there were considerably more males than females with Indigenous status unknown (due to item non-response) in the Northern Territory.

	Males		Females		Total
	no.	%	no.	%	no.
New South Wales	46 626	49.2	48 210	50.8	94 836
Victoria	38 194	49.3	39 310	50.7	77 504
Queensland	27 281	49.2	28 188	50.8	55 469
South Australia	10 279	48.0	11 130	52.0	21 409
Western Australia	13 714	49.9	13 771	50.1	27 485
Tasmania	3 682	49.4	3 766	50.6	7 448
Northern Territory	1 532	56.8	1 167	43.2	2 699
Australian Capital Territory	1 585	50.8	1 535	49.2	3 120
Australia(c)	142 918	49.3	147 104	50.7	290 022
(a) Usual residence Census counts. Excludes overseas visitors. (b) Excludes imputed records. (c) Includes Other Territories.
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).

Census form type

13 An Interviewer Household Form is used in discrete Aboriginal and Torres Strait Islander communities. Very few people who were enumerated using the Interviewer Household Form had an unknown Indigenous status. Of the 83,900 people whose response in the 2011 Census was collected using the Interviewer Household Form, 0.5% (450 records) had an unknown Indigenous status. This was lower than in 2006 (0.7%).

Response to other Census questions

14 Responses to other Census questions may indicate that a record with a non-response for the Indigenous status question is likely to be for an Aboriginal and/or Torres Strait Islander person. In the 2011 Census there were 1,000 records with no response to the Indigenous status question, but with an Australian Aboriginal or Torres Strait Islander ancestry reported. The ABS does not edit these records to change Indigenous status during processing.

15 Of those people for whom a response to the Indigenous status question was not reported, 14% (40,700 records) did not have a response to any questions about birthplace, ancestry, language spoken at home or religious affiliation.