3302.0.55.003 - Life Tables for Aboriginal and Torres Strait Islander Australians, 2010-2012  
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Contents >> Data linkage to derive Aboriginal and Torres Strait Islander deaths identification rates >> Use of the CDE study to derive Aboriginal and Torres Strait Islander deaths identification rates

This document was added 11/22/2013.



USE OF THE CDE STUDY TO DERIVE ABORIGINAL AND TORRES STRAIT ISLANDER DEATHS IDENTIFICATION RATES

The CDE study allows a direct comparison of Indigenous status recorded on the death registration and the Census data for what is highly likely to be the same individual, and enables estimation of the undercoverage of Aboriginal and Torres Strait Islander deaths in the death registration system. Table 3.3 presents the outcomes of the CDE study for Aboriginal and Torres Strait Islander deaths in Australia. It provides a cross-classification of the linked death registrations and Census records by the Indigenous status and age groups recorded in the respective records. Similar tables for other states and territories (without an age breakdown) where there are sufficient deaths available are in data cube Table 3: Summary of Aboriginal and Torres Strait Islander deaths by Indigenous status, Selected states and territories and Australia - 2011-2012 (cat. no. 3302.0.55.003).

3.3 SUMMARY OF LINKED DEATHS BY INDIGENOUS STATUS, Australia - 2011-2012

DEATH REGISTRATION CLASSIFICATION
Aboriginal and Torres Strait Islander
Non-Indigenous
Not stated
Total
Census classification
no.
no.
no.
no.

0-14 years
Aboriginal and Torres Strait Islander
36
12
2
50
Non-Indigenous
2
420
7
429
Not stated
2
16
-
18
Total
40
448
9
497
15-59 years
Aboriginal and Torres Strait Islander
751
206
18
975
Non-Indigenous
72
14 357
122
14 551
Not stated
22
347
5
374
Total
845
14 910
145
15 900
60 years and over
Aboriginal and Torres Strait Islander
763
360
8
1 131
Non-Indigenous
201
118 242
578
119 021
Not stated
35
6 077
36
6 148
Total
999
124 679
622
126 300
All ages
Aboriginal and Torres Strait Islander
1 550
578
28
2 156
Non-Indigenous
275
133 019
707
134 001
Not stated
59
6 440
41
6 540
Total
1 884
140 037
776
142 697

- nil or rounded to zero (including null cells)


The table highlights a number of features:
  • of the 2,156 linked records identified as Aboriginal and Torres Strait Islander on the Census file, only 1,550 (72%) were identified as Aboriginal and Torres Strait Islander on the death registration;
  • the 1,550 records identified as Aboriginal and Torres Strait Islander in both datasets represented 82% (that is 1,550 / 1,884 * 100) of linked deaths identified as Aboriginal and Torres Strait Islander in death registrations;
  • there is misidentification of Indigenous status between the Census and death registrations (for example, Aboriginal and Torres Strait Islander in death registrations but non-Indigenous in Census, and vice versa);
  • the overall Aboriginal and Torres Strait Islander deaths identification rate, indicated by these statistics, is 87% (that is, 1,884 / 2156 * 100).

The above suggests that while there appears to be misidentification of Indigenous status between the Census and death registrations, the overall identification rate in the death registrations collection is quite high at the national level (87%).

At the same time, it needs to be recognised that at the national level, about 20% of Aboriginal and Torres Strait Islander deaths as recorded on the death registration form could not be linked to a Census record. This would occur due to missing or inconsistent information in the fields being used for linking and also undercount of the Aboriginal and Torres Strait Islander population in the Census counts. Despite these issues, it is considered that the linked data provide reasonable estimates of the identification rate of Aboriginal and Torres Strait Islander deaths.

For the purpose of compiling Aboriginal and Torres Strait Islander life tables, the Aboriginal and Torres Strait Islander ERP used was derived from Census counts adjusted by results of the Post Enumeration Survey (PES). The PES provides an independent check on Census coverage and also identifies key demographic characteristics of the population that have been missed or overcounted in the Census. In compiling Aboriginal and Torres Strait Islander ERP, Indigenous status reported by the PES was considered more reliable than that recorded in the Census.

Therefore, to be consistent with Aboriginal and Torres Strait Islander ERP calculations, the number of deaths reported as Aboriginal and Torres Strait Islander in Census in the CDE linked data were adjusted to a PES basis. It should be noted that these adjustments were only in respect of misclassifications of Indigenous status in the linked file. No attempt was, or could be, made for undercount identified in the PES; this is reflected in the non-matched death registrations.

Thus, the Aboriginal and Torres Strait Islander deaths identification rate using the linked data was derived by:
      1. calculating the propensities, from PES, of being Aboriginal and Torres Strait Islander in PES given Census Indigenous status (to align the Census Indigenous status with the PES Indigenous status);
      2. applying the propensities to counts from the CDE linked data to obtain the expected number of deaths in Census on a PES basis; and
      3. taking the ratio of the number of deaths reported as Aboriginal and Torres Strait Islander in death registrations to that reported in Census on a PES basis to calculate the Aboriginal and Torres Strait Islander deaths identification rate.

The following step by step example illustrates the calculation of the identification rate of Aboriginal and Torres Strait Islander deaths for Australia using the improved method that include age-specific identification rates when calculating the underidentification adjustment.


Step 1: Calculation of propensities from PES data given in table 3.4

The propensities are calculated for persons who matched to Census and responded as Aboriginal and Torres Strait Islander in the PES to the Census Indigenous status question. They were estimated by the three response classes for the Census Indigenous status question: Aboriginal and Torres Strait Islander, non-Indigenous and not stated.

3.4 INDIGENOUS STATUS AS REPORTED IN 2011 CENSUS AND 2011 POST ENUMERATION SURVEY(a), Australia

PES RESPONSE
Aboriginal and Torres Strait Islander
Non-Indigenous
Total
Census classification
no.
no.
no.

0-14 years
Aboriginal and Torres Strait Islander
1 641
98
1 739
Non-Indigenous
59
15 061
15 120
Not stated
32
290
322
Total
1 732
15 449
17 181
15-59 years
Aboriginal and Torres Strait Islander
2 497
141
2 638
Non-Indigenous
197
47 000
47 197
Not stated
33
524
557
Total
2 727
47 665
50 392
60 years and over
Aboriginal and Torres Strait Islander
263
28
291
Non-Indigenous
27
14 544
14 571
Not stated
8
368
376
Total
298
14 940
15 238
All ages
Aboriginal and Torres Strait Islander
4 401
267
4 668
Non-Indigenous
283
76 605
76 888
Not stated
73
1 182
1 255
Total
4 757
78 054
82 811

(a) This tables uses unweighted data for illustrative purposes. Weighted PES data was used when determining the propensities for calculating life tables.


The following example will refer to data for the 0-14 years age group in table 3.4:
  • P(ATSI/ATSI) = propensity of being Aboriginal and Torres Strait Islander in PES given Census Indigenous status is 'Aboriginal and Torres Strait Islander' is 1,641 / 1,739 = 0.9436
  • P(ATSI/NI) = propensity of being Aboriginal and Torres Strait Islander in PES given Census Indigenous status is 'non-Indigenous' is 59 / 15,120 = 0.0039
  • P(ATSI/NS) = propensity of being Aboriginal and Torres Strait Islander in PES given Census Indigenous status is 'not stated' is 32 / 322 = 0.0994

The above propensities are based on the unweighted PES data. In calculating Aboriginal and Torres Strait Islander ERP, weighted PES information was used. Therefore, to be consistent with Aboriginal and Torres Strait Islander ERP calculations, the propensities were calculated using the weighted PES data. This gave P(ATSI/ATSI) = 0.9088, P(ATSI/NI) = 0.0032 and P(ATSI/NS) = 0.0882.

The Australia level propensities P(ATSI/NI) and P(ATSI/NS) calculated above are based on relatively small numbers of PES responses (59 and 32 respectively for the 0-14 years age group). These propensities calculated at the state/territory level, while not disaggregated by age, are still unreliable as they are based on considerably smaller numbers of PES responses. To overcome this problem, national level P(ATSI/NI) and P(ATSI/NS) are used for the states and territories (though without any disaggregation by age, as outlined under Calculation of adjustment factor for the states and territory).


Step 2: Estimation of expected number of deaths in Census in linked data given in table 3.3 using PES Aboriginal and Torres Strait Islander propensities

The expected number of deaths in the Census in CDE linked data file, for persons aged 0-14 years, using PES Aboriginal and Torres Strait Islander propensities is:
  • = 50 * P(ATSI/ATSI) + 429 * P(ATSI/NI) + 18 * P(ATSI/NS)
  • = 50 * 0.9088 + 429 * 0.0032 + 18 * 0.0882
  • = 48

where the numbers 50, 429 and 18 are Aboriginal and Torres Strait Islander, non-Indigenous and not stated deaths in Census for the 0-14 years age group (table 3.3).


Step 3: Calculation of identification rate of Aboriginal and Torres Strait Islander deaths, Australia

The estimate of the Aboriginal and Torres Strait Islander deaths identification rate is then calculated by taking the ratio of the number of deaths reported as Aboriginal and Torres Strait Islander in death registrations to the number of deaths expected to be recorded as Aboriginal and Torres Strait Islander in Census using the PES Aboriginal and Torres Strait Islander propensities:

= 40 / 48

= 0.83

where 40 is the Aboriginal and Torres Strait Islander deaths in death registrations for the 0-14 years age group (table 3.3).


Step 4: Calculation of adjustment factor, Australia

The adjustment factor is taken to be the reciprocal of the identification rate of Aboriginal and Torres Strait Islander deaths:

= 1 / 0.83

= 1.21

In the linked data, 40 records for the 0-14 years age group were reported as Aboriginal and Torres Strait Islander on the death registration form (table 3.3). Of deaths linked to the Census, 48 were recorded as Aboriginal and Torres Strait Islander, after adjustment for classifying Indigenous status in the way that PES does. This means that fewer deaths were identified as Aboriginal and Torres Strait Islander in death registrations than were expected in Census on a PES basis. Therefore, for the 0-14 age group, the number of Aboriginal and Torres Strait Islander deaths according to death registrations needed multiplying by an adjustment factor of 1 / 0.83 = 1.21 to be comparable to the Aboriginal and Torres Strait Islander deaths expected to be recorded as such in the Census on a PES basis.

Steps 1-4 were repeated to calculate identification rates for the 15-59 and 60+ age groups. Identification rates were 0.89 and 0.78 for the 15-59 and 60+ age groups respectively.

3.5 ABORIGINAL AND TORRES STRAIT ISLANDER IDENTIFICATION RATES, Headline Australia(a) - 2011-2012

0-14
15-59
60+
Total(b)

Identification Rate
0.83
0.89
0.78
0.82
Adjustment Factor(c)
1.21
1.12
1.29
1.21

(a) Headline estimates for Australia are calculated using an improved methodology (taking into account age-specific identification rates) that could not be applied at the state and territory or remoteness area levels. Therefore this data should not be compared with data for any state or territory, or remoteness area.
(b) Total included here as a summary comparison measure, since the rates were applied at the age group level.
(c) Calculated as the reciprocal of the identification rate.



Calculation of adjustment factor for the states and territory

The procedure described above was used to derive Aboriginal and Torres Strait Islander deaths identification rates at the Australia level only. Identification rates for states, territories and remoteness areas were calculated using a similar method but without using age-specific identification rates. This method is detailed fully in Chapter 3 of Experimental Life Tables for Aboriginal and Torres Strait Islander Australians 2005-2007 (cat. no. 3302.0.55.003).

Due to small numbers of Aboriginal and Torres Strait Islander deaths in Victoria, South Australia, Tasmania and the Australian Capital Territory, it was not feasible to derive separate Aboriginal and Torres Strait Islander deaths identification rates for these jurisdictions. Therefore, a single Aboriginal and Torres Strait Islander deaths identification rate was derived by grouping these together. The ABS is continuing to explore methodological options for creating life tables for these jurisdictions by combining with, and borrowing strength from, one or more of the published states and territories. This investigation continues with the ambition of using such life tables for backcasting and projections purposes. If a method cannot be determined in time for use in the backcasting and projections due for release in April 2014, the ABS will continue with the established method of using New South Wales measures as a proxy for Victoria, Tasmania and the Australian Capital Territory, and Western Australia as a proxy for South Australia.

There is considerable variation in the identification rates at the state/territory level (table 3.6). The estimate is less than 1.0 for New South Wales, Queensland, Western Australia and the Victoria/South Australia/Tasmania/Australian Capital Territory grouping, which indicates a level of under-identification of Aboriginal and Torres Strait Islander deaths in death registrations relative to the Census on a PES basis. The situation is the opposite for the Northern Territory, indicating a slight over-representation of Aboriginal and Torres Strait Islander deaths in death registrations relative to the Census for linked records; that is, persons who are identified as Aboriginal and Torres Strait Islander in the death registrations collection exceed those identified as Aboriginal and Torres Strait Islander in the Census on a PES basis. There is no clear reason as to why this might be the case, although there is evidence that some Aboriginal and Torres Strait Islander deaths have a state of usual residence on the death registration that is different to the Census. It should be noted that the Northern Territory had higher levels of unlinked Aboriginal and Torres Strait Islander death records (21%) thank other jurisdictions, which in part is a reflection of the high Census undercount for this jurisdiction. This may indicate that the linked records may not be entirely representative of all death records.

3.6 ABORIGINAL AND TORRES STRAIT ISLANDER IDENTIFICATION RATES, State/territory and Australia - 2011-2012

Aboriginal and Torres Strait Islander deaths according to death registrations
Expected number of Aboriginal and Torres Strait Islander deaths(a)
Identification rate
Adjustment factor(b)
State/territory
no.
no.
no.
no.

NSW
604
859
0.70
1.42
Qld
520
647
0.80
1.24
WA
276
314
0.88
1.14
NT
262
251
1.04
0.96
Vic./SA/Tas./ACT/OT combined
222
554
0.40
2.49
Aust.(c)(d)
1 884
2 625
0.72
1.39

(a) In Census if weighted PES Aboriginal and Torres Strait Islander propensities are used.
(b) Calculated as the reciprocal of the identification rate.
(c) These estimates are not the headline estimates for Australia, because they are calculated without an age-adjustment, but are provided to enable effective comparison with the state and territory, and remoteness area estimates.
(d) Includes all states and territories.


There is quite considerable variation in the identification rates by remoteness (table 3.7). The estimates of 0.56 for Major Cities and Inner Regional remoteness areas indicates a high level of under-identification of Aboriginal and Torres Strait Islander deaths in death registrations. In contrast, the identification rate if just 0.96 for Outer Regional, Remote and Very Remote areas, indicating a much lower level of under-identification.

3.7 ABORIGINAL AND TORRES STRAIT ISLANDER IDENTIFICATION RATES, Remoteness Areas - 2011-2012

Aboriginal and Torres Strait Islander deaths according to death registrations
Expected number of Aboriginal and Torres Strait Islander deaths(a)
Identification rate
Adjustment factor(b)
Remoteness Area
no.
no.
no.
no.

Major Cities and Inner Regional
919
1 627
0.56
1.77
Outer Regional, Remote and Very Remote
965
1 003
0.96
1.04
Aust.(c)(d)
1 884
2 625
0.72
1.39

(a) In Census if weighted PES Aboriginal and Torres Strait Islander propensities are used.
(b) Calculated as the reciprocal of the identification rate.
(c) These estimates are not the headline estimates for Australia, because they are calculated without an age-adjustment, but are provided to enable effective comparison with the state and territory, and remoteness area estimates.
(d) Includes all states and territories.


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