3238.0 - Estimates and Projections, Aboriginal and Torres Strait Islander Australians, 2006 to 2031  
Latest ISSUE Released at 11:30 AM (CANBERRA TIME) 11/07/2019   
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ASSUMPTIONS

The Australian Bureau of Statistics (ABS) uses a cohort-component method for producing population projections for the period 2017-2031, based on the 2016 Census of Population and Housing. Using this method, assumptions made about future levels of fertility, mortality, and migration are applied to the 2016 Census base population (split by sex and single year of age) to obtain a projected population for the following year. The assumptions are then applied to this new (projected) population to obtain a projected population for the next year. This process is repeated until the end of the projection period is reached.

A similar method can also be used to produce population 'backcast' estimates which span the period 2006-2016. This technique requires assumptions to be made about past levels of mortality taking into account the most recent 2016 Census data to utilise the best quality estimates available. These are applied to the 2016 base population to obtain a 'reverse-survived' population for the previous year. The assumptions are then applied to this new reverse-survived population to obtain a population for the preceding year. This process is repeated until the first year of the estimation period is reached.

Estimates and projections presented in this release supersede estimates and projections based on earlier censuses. The assumptions used differ from those in previous publications. As a result, and in addition to the use of a different base population, which is significantly larger than the previous base population, the size, structure and components of the estimated and projected Aboriginal and Torres Strait Islander population are different to those previously published for the same period.


Span of estimates and projections
  • Backcast estimates of the Aboriginal and Torres Strait Islander population in this release span the period 30 June 2006 to 30 June 2016 and are available for Australia, the States and Territories and Remoteness Areas.
  • Projections of the Aboriginal and Torres Strait Islander population in this release span the period 30 June 2017 to 30 June 2031 and are available for Australia, States and Territories, Indigenous Regions and Remoteness Areas.

Given the large interval for which the assumptions are applied, backcast and projections data should be interpreted with caution.

Base population
  • The base population is the Aboriginal and Torres Strait Islander estimated resident population of Australia at 30 June 2016, derived from 2016 Census counts of Aboriginal and Torres Strait Islander Australians, adjusted for net undercount as measured by the Post Enumeration Survey (PES).


ESTIMATES

Summary of assumptions

A single time series of Aboriginal and Torres Strait Islander estimates for the period 2006 to 2016 has been produced.

Over this period life expectancy at birth is assumed to:
  • increase by 0.40 years per year for males and 0.25 years per year for females between 2011-2016
  • increase by 0.30 years per year for males and 0.20 years per year for females between 2006-2011.

Net interstate migration for each of the above two intercensal periods was based on levels observed in each respective intercensal period.

Zero net overseas migration occurred across the entire series with no arrivals and departures.


PROJECTIONS

Summary of projections

Assumptions have been formulated on the basis of past demographic trends, in conjunction with consultation with various experts and government department representative at the national and state/territory level. They do not attempt to allow for non-demographic factors (such as major government policy decisions, economic factors, natural disasters, epidemic or significant health treatment improvements) which may alter future demographic behaviour or outcomes.


Table 1: SUMMARY OF ASSUMPTIONS

Total fertility rate
Total paternity rate
Male life expectancy at birth
Female life expectancy at birth
babies per woman
babies per man
years
years

High assumption
Constant fertility rates
Annual increase of 2.0%
Annual increase of 0.45 years
Annual increase of 0.35 years
Medium assumption
Annual decrease of 1.0%
Annual increase of 1.0%
Annual increase of 0.40 years
Annual increase of 0.25 years
Low assumption
Annual decrease of 1.5%
Constant paternity rates
Annual increase of 0.25 years
Annual increase of 0.20 years


Additional assumptions regarding the remaining demographic factors for the projections are:
  • constant interstate migration at levels observed in the 2016 Census
  • zero net overseas migration with no arrivals and no departures
  • zero unexplained growth in Aboriginal and Torres Strait Islander population.


Projections series

By considering the above assumptions, nine projection series were produced. Three main series have been selected from these to provide a range of projections for analysis and discussion in this publication. These series are referred to as series A (high), series B (medium) and series C (low). Detailed information on these and the remaining projection series are available in the data cubes.


Table 2: PROJECTION SERIES, Assumptions used (a)

Life expectancy at birth
Low increase
Medium increase
High increase

CONSTANT PATERNITY RATES
Fertility rates
Constant
. .
. .
Annual decrease of 1.0%
. .
F
. .
Annual decrease of 1.5%
C
. .
. .

1% ANNUAL INCREASE IN PATERNITY RATES
Fertility rates
Constant
. .
D
. .
Annual decrease of 1.0%
I
B
H
Annual decrease of 1.5%
. .
E
. .

2% ANNUAL INCREASE IN PATERNITY RATES
Fertility rates
Constant
. .
. .
A
Annual decrease of 1.0%
. .
G
. .
Annual decrease of 1.5%
. .
. .
. .

. . not applicable
(a) Levels of interstate migration as observed in the 2016 Census and zero overseas migration apply to all series.

Which series to use

The three main series respectively imply a high, medium and low overall growth rate of the Aboriginal and Torres Strait Islander population. It is expected that series B will be the most appropriate choice for most users. The ABS will be using series B in calculating fertility and mortality rates for inclusion in the annual Births and Deaths publications.

The effect of alternative assumptions on the size of the future Aboriginal and Torres Strait Islander population is described in the Chapter: Sensitivity to Projection Assumptions.

The population projections are not intended as forecasts or predictions, but are illustrations of growth and change in the population that would occur if assumptions made about future demographic trends were to prevail over the projection period. Future uncertainty, along with the subjective nature of assessing current trends, means that using a range of possible outcomes rather then a single projection series acknowledges a range of the possible future size, distribution and age structure of Australia's Aboriginal and Torres Strait Islander population.

There is also some level of uncertainty surrounding 2016 Aboriginal and Torres Strait Islander Census counts and population estimates on which the projections are based, as well as data quality issues relating to registered births and deaths of Aboriginal and Torres Strait Islander people. Information on data quality issues related to Aboriginal and Torres Strait Islander estimates and projections are available in the Quality Declaration.


FERTILITY AND PATERNITY

The ABS Births collection identifies a birth as being an Aboriginal and/or Torres Strait Islander person where at least one parent identifies themselves as being of Aboriginal and Torres Strait Islander origin on the birth registration. These can be attributed to either:
  • Aboriginal and Torres Strait Islander mothers, including births where both the mother and father are Aboriginal and Torres Strait Islander
  • Aboriginal and Torres Strait Islander fathers and non-Indigenous mothers.

For simplicity, birth rates of Aboriginal and Torres Strait Islander mothers are referred to in this release as fertility rates, while birth rates where the father is Aboriginal and Torres Strait Islander and the mother's Indigenous status is non-Indigenous or not stated are referred to as paternity rates.

To produce population projections using the cohort-component, method, assumptions for each year of the projection period are required for age-specific fertility rates, age-specific paternity rates and the Aboriginal and Torres Strait Islander sex ratio at birth.


Indigenous status of parents

Of the Aboriginal and Torres Strait Islander births registered in 2017:
  • 27% were births for which both parents identified themselves as being of Aboriginal and Torres Strait Islander origin on the birth certificate statement
  • 43% were births where only the mother was of Aboriginal and Torres Strait Islander origin (including births where paternity was not acknowledged or the father's Indigenous status was not stated)
  • 30% were births where only the father was of Aboriginal and Torres Strait Islander origin (including births where the mother's Indigenous status was not stated).


Graph Image for Graph 1 - Indigenous status of parents, 2001-2017

Footnote(s): (a) Includes fathers whose Indigenous status was not stated. (b) Includes mothers whose Indigenous status was not stated.

Source(s): Births Australia, 2017 (cat. no. 3301.0)




The proportion of Aboriginal and Torres Strait Islander births attributed to Aboriginal and Torres Strait Islander mothers and/or Aboriginal and Torres Strait Islander fathers differs considerably between the states and territories.

In 2017:
  • The Northern Territory had the highest proportion of births (43%) where both the mother and father were Aboriginal and Torres Strait Islander
  • Tasmania had the lowest proportion of births (12%) where both mother and father were Aboriginal and Torres Strait Islander
  • 39% of births in the Australian Capital Territory were to non-Indigenous mothers and Aboriginal and Torres Strait Islander fathers (11% in the Northern Territory).


Graph Image for Graph 2 - Indigenous status of parents, states and territories, 2017

Footnote(s): (a) Includes fathers whose Indigenous status was not stated. (b) Includes mothers whose Indigenous status was not stated. (c) Includes Other Territories.

Source(s): Births Australia, 2017 (cat. no. 3301.0)




Sex ratio at birth

Population projections require an assumed sex ratio at birth in order to split total projected births into male and female births. The sex ratio for Aboriginal and Torres Strait Islander births registered in Australia fluctuates around 103 to 109 male births per 100 female births. A constant ratio of 105.6 males per 100 female births has been assumed for the duration of the projection period.


FERTILITY ASSUMPTION

Three main assumptions have been made for future fertility rates of Aboriginal and Torres Strait Islander women:
  • Constant fertility rates at the 2017 level
  • An annual decline of 1.0% in fertility rates
  • An annual decline of 1.5% in fertility rates.

These assumptions were primarily chosen on the basis of the declining trend in fertility as indicated by data from the 'children ever born' question asked in the Census.

The same rate of decline in fertility rates have been assumed for each state and territory, Indigenous Regions and Remoteness Area.


Trends in fertility rates

Children ever born

Cohort fertility rates, based on the 'children ever born' question asked in the Census illustrate a decline in Aboriginal and Torres Strait Islander fertility over time.

The number of children ever born provides information on actual fertility outcomes of women of different ages. In particular, the number of children ever born to women aged 40-44 year can be regarded as a measure of completed fertility; that is, on average how many children this group of women each had throughout their entire reproductive lifetimes.

Aboriginal and Torres Strait Islander women aged 40–44 years had on average:
  • 3.97 babies per woman in the 1986 Census
  • 3.10 babies per woman in he 1996 Census
  • 2.84 babies per woman in the 2006 Census
  • 2.82 babies per woman in the 2011 Census
  • 2.77 babies per woman in the 2016 Census

The average number of children ever born to Aboriginal and Torres Strait Islander women has been declining for each age group over the past three decades. These declines, particularly in the younger age groups, indicate probable declines in the future overall level of Aboriginal and Torres Strait Islander fertility.

Graph Image for Graph 3 - Average number of children ever born to Aboriginal and Torres Strait women, Census years(a)(b)

Footnote(s): (a) Average number of children ever born calculated on assumption that women with 6 or more children had an average of 6.9 children. (b) The children ever born question was not asked in the 1991 and 2001 Censuses.

Source(s): 1986,1996, 2006, 2001 and 2016 Censuses of Population and Housing



Total fertility rate

The total fertility rate (TFR), based on birth registrations, represents the average number of children a woman could expect to bear during her lifetime if she experienced current age-specific fertility rates at each age of her reproductive life.

The TFR for Aboriginal and Torres Strait Islander women:
  • Was 1.9 babies per woman in 2001
  • Gradually increased to 2.5 in 2010, before slowly decreasing over the period 2012-2016
  • By 2017, increased to 2.3 babies per woman.

Graph Image for Graph 4 - Total fertility rates, Australia, 2001-2017


Choice of fertility assumption

In summary, while fertility rates based on birth registrations of Aboriginal and Torres Strait Islander children may provide some evidence for assuming constant or increasing Aboriginal and Torres Strait Islander fertility, cohort fertility rates based on the 'children ever born' question asked in the Census indicate long-term declines. Assumptions that take both sets of evidence into account have been made but with more emphasis given to the 'children ever born' data.
  • Low series: The magnitude and duration of any future changes in fertility rates are not possible to gauge accurately, but it's possible that a decline observed between 2012 to 2016 may continue during the projection period. On this basis, low series assumes an annual decline of 1.5%.
  • Medium series: assumes an annual decline of 1% which is equivalent to the decline in average children per Aboriginal and Torres Strait Islander woman in the last ten years.
  • High series: assumes constant fertility rate as observed in 2017.


Method used to produce fertility assumptions

Assumed age-specific fertility rates for Aboriginal and Torres Strait Islander women are based on three years of birth registrations (2015 to 2017) in order to minimise the effect of year-to-year fluctuations in registrations. These rates were adjusted to produce plausible numbers of projected births in the first year of the projection period in accordance with Aboriginal and Torres Strait Islander population estimates at younger ages.

Adjustment factors were calculated for each state and territory by taking the ratio of the number of Aboriginal and Torres Strait Islander children aged 0,1 and 2 at 30 June 2016 to the number of births registered between 2015 and 2017. Differences in the two sources can be attributed to several factors, including:
  • net undercount
  • Census records for which Indigenous status was not stated
  • lags in the registration of births
  • differences in the method of identification between the Census and the Birth registration collection (for example, identified as Aboriginal and Torres Strait Islander in the birth registration but not on the Census form).

As rates are required on a financial year basis they were adjusted to account for the six-month period between the mid-point of the period 2015–17 (calendar year fertility rates) and 2016–17 (financial year fertility rates).

Assumed declines in fertility rates are applied uniformly across relevant age groups.




Table 3: ASSUMED FERTILITY RATES, States and territories

AGE-SPECIFIC FERTILITY RATES(a)
15–19(b)
20–24
25–29
30–34
35–39
40–44
45–49(c)
TFR(d)

YEAR ENDED 30 JUNE 2017

NSW
44.9
114.4
121.0
88.7
45.5
9.1
0.3
2.12
Vic.
35.7
101.3
105.7
89.1
43.4
13.4
0.6
1.95
Qld
51.3
127.4
122.2
91.0
46.1
11.0
0.8
2.25
SA
49.5
110.8
115.6
84.1
46.9
7.4
0.5
2.07
WA
68.8
131.0
118.8
78.6
41.7
10.4
0.4
2.25
Tas.
30.3
101.7
97.1
75.3
34.9
5.5
1.72
NT
63.8
123.0
103.0
74.5
38.6
8.0
0.4
2.06
ACT
23.8
77.2
78.5
92.2
46.4
14.1
1.8
1.67
Aust.(e)
50.5
119.5
116.7
85.6
44.0
9.9
0.5
2.13

YEAR ENDED 30 JUNE 2031

NSW
39.0
99.4
105.1
77.0
39.5
7.9
0.3
1.84
Vic.
31.0
88.0
91.8
77.4
37.7
11.6
0.5
1.69
Qld
44.6
110.7
106.2
79.0
40.0
9.6
0.7
1.95
SA
43.0
96.2
100.4
73.1
40.8
6.4
0.5
1.80
WA
59.8
113.8
103.2
68.3
36.2
9.0
0.3
1.95
Tas.
26.4
88.4
84.4
65.4
30.3
4.8
1.50
NT
55.5
106.8
89.4
64.7
33.5
6.9
0.4
1.79
ACT
20.7
67.1
68.2
80.1
40.3
12.2
1.6
1.45
Aust.(e)
43.8
103.8
101.4
74.4
38.2
8.6
0.4
1.85

- nil or rounded to zero (including null cells)
(a) Births per 1,000 Aboriginal and Torres Strait Islander women.
(b) Includes births to mothers aged less than 15 years.
(c) Includes births to mothers aged 50 years and over.
(d) Births per Aboriginal and Torres Strait Islander woman.
(e) Includes Other Territories.


Regional variations in fertility

Indigenous Regions

The projections in this release apply fertility assumptions for sub-state geographies by aggregating Indigenous Regions (IREGs) into two groups for each state and territory (except Tasmania and the Australian Capital Territory):
  • capital city IREG (for example, Adelaide IREG)
  • rest of state/territory IREGs combined (for example, Port Augusta IREG and Port Lincoln - Ceduna IREG combined).
  • Fertility rates for each of these groups were adjusted in a similar manner to state and territory rates to produce plausible numbers of projected births in the first year of the projection period in accordance with Aboriginal and Torres Strait Islander population estimates at younger ages.


Table 4: ASSUMED TOTAL FERTILITY RATES(a), Indigenous Regions

30 June 2017
30 June 2031

Sydney IREG
1.85
1.60
Rest of NSW
2.26
1.96
Melbourne IREG
1.58
1.37
Rest of Vic.
2.38
2.07
Brisbane IREG
1.89
1.64
Rest of Qld
2.48
2.15
Adelaide IREG
2.02
1.76
Rest of SA
2.23
1.94
Perth IREG
2.13
1.85
Rest of WA
2.35
2.04
Tasmania IREG
1.72
1.50
Darwin IREG
2.03
1.77
Rest of NT
2.08
1.81
ACT IREG
1.67
1.46
Australia(b)
2.13
1.85

(a) Births per Aboriginal and Torres Strait Islander woman.
(b) Includes Other Territories.


Remoteness Areas

Assumed fertility rates for Remoteness Areas were calculated and adjusted using the same technique as for the states and territories.


Table 5: ASSUMED TOTAL FERTILITY RATES(a), Remoteness Areas

30 June 2017
30 June 2031

Major Cities
1.87
1.62
Inner and Outer Regional
2.31
2.00
Remote and Very Remote
2.30
2.00
Australia(b)
2.13
1.85

(a) Births per Aboriginal and Torres Strait Islander woman.
(b) Includes Other Territories.


PATERNITY ASSUMPTIONS

The total paternity rate (TPR) is defined as the average number of Aboriginal and Torres Strait Islander babies born per Aboriginal and Torres Strait Islander father where the mother's Indigenous status is non-Indigenous or not stated, and is calculated in the same way as the TFR.

Three main assumptions have been made for future paternity rates:
  • constant paternity rates
  • an annual increase of 1.0% in paternity rates
  • an annual increase of 2.0% in paternity rates.

The same rate of increase in paternity rates has been assumed for each state and territory, Indigenous Region, and Remoteness Area.


Trends in paternity rates

As with the TFR, the time series of the TPR is based on population estimates which are not strictly comparable over time. Based on birth registrations, the TPR has been slowly increasing over more than a decade, from 0.77 births per Aboriginal and Torres Strait Islander male in 2001 to 1.06 in 2017.

Graph Image for Graph 5 - Total paternity rates(a)(b), Australia, 2001-2017

Footnote(s): (a) Births to Aboriginal and Torres Strait Islander males, where the mother's Indigenous status was non-Indigenous or not stated. The TPR is calculated in the same way as the TFR. (b) Estimated resident population based on the 2011 Census.

Source(s): Graph 5 - Total paternity rates(a)(b), Australia, 2001-2017-Graph 5 Total paternity rates 2001 to 2017



Choice of paternity assumption

The 'children ever born' question is not asked of males in the Census. Therefore, there is no reliable source other than birth registrations for calculating paternity rate.
  • Low series: assumes constant paternity rate over the projection period.
  • Medium series: paternity rate calculated from birth registration data has been slowly increasing over time and showed an increase of 1.1% during 2006-2016. To reflect this trend, medium series assumes an annual increase of 1% in paternity rate.
  • High series: the increase in paternity rate in the recent years might have been underestimated due to registration lags. Therefore, an annual increase in paternity rate of 2% is assumed for high series.


Method used to produce paternity assumptions

Assumed age-specific paternity rates for Aboriginal and Torres Strait Islander men are based on three years of birth registrations (2015 to 2017) where the mother's Indigenous status is non-Indigenous or not stated, which were then adjusted to ensure consistency with the Aboriginal and Torres Strait Islander population at younger ages. Assumed increases in paternity rates are applied uniformly across relevant age groups.


Table 6: ASSUMED PATERNITY RATES, States and territories

AGE-SPECIFIC PATERNITY RATES(a)
15-19(b)
20-24
25-29
30-34
35-39
40-44
45-49(c)
TPR(d)

YEAR ENDED 30 JUNE 2017

NSW
9.0
40.5
61.8
62.5
41.6
16.1
8.6
1.20
Vic.
8.9
44.6
59.9
76.8
50.4
22.1
16.0
1.39
Qld
7.3
35.5
47.7
50.6
34.2
13.6
6.8
0.98
SA
7.7
33.4
48.6
42.1
30.0
14.8
5.4
0.91
WA
5.9
20.3
28.8
32.6
21.8
9.0
4.7
0.62
Tas.
9.2
44.6
77.3
69.5
48.1
23.9
7.7
1.40
NT
0.4
6.0
11.3
10.9
7.9
3.3
3.2
0.21
ACT
8.1
33.1
50.3
90.9
54.2
15.5
8.1
1.30
Aust.(e)
7.2
32.9
46.6
48.6
32.8
13.5
7.3
0.94

YEAR ENDED 30 JUNE 2031

NSW
10.3
46.6
71.0
71.8
47.8
18.5
9.9
1.38
Vic.
10.3
51.3
68.9
88.2
58.0
25.4
18.4
1.60
Qld
8.4
40.8
54.8
58.2
39.3
15.6
7.8
1.12
SA
8.8
38.4
55.8
48.4
34.5
17.0
6.2
1.05
WA
6.8
23.4
33.1
37.4
25.1
10.3
5.3
0.71
Tas.
10.5
51.3
88.9
79.9
55.3
27.4
8.9
1.61
NT
0.5
6.9
12.9
12.5
9.1
3.7
3.6
0.25
ACT
9.3
38.0
57.8
104.5
62.3
17.8
9.3
1.50
Aust.(e)
8.3
37.8
53.5
55.9
37.7
15.5
8.4
1.09

(a) Births to Aboriginal and Torres Strait Islander men, where the mother's Indigenous status was non-Indigenous or not stated, per 1,000 Aboriginal and Torres Strait Islander men.
(b) Includes births to fathers aged less than 15 years.
(c) Includes births to fathers aged 50 years and over.
(d) Births to Aboriginal and Torres Strait Islander men, where the mother's Indigenous status was non-Indigenous or not stated, per Aboriginal and Torres Strait Islander man.
(e) Includes Other Territories.


Regional variations in paternity

Indigenous Regions

Assumed paternity rates for IREGs were calculated and adjusted using the same technique as for the states and territories.


Table 7: ASSUMED TOTAL PATERNITY RATES(a), Indigenous Regions

30 June 2017
30 June 2031

Sydney IREG
1.15
1.33
Rest of NSW
1.22
1.40
Melbourne IREG
1.19
1.37
Rest of Vic.
1.64
1.88
Brisbane IREG
1.31
1.50
Rest of Qld
0.78
0.90
Adelaide IREG
1.10
1.27
Rest of SA
0.49
0.57
Perth IREG
0.82
0.95
Rest of WA
0.47
0.54
Tasmania IREG
1.40
1.61
Darwin IREG
0.53
0.61
Rest of NT
0.08
0.10
ACT IREG
1.30
1.50
Australia(b)
0.94
1.09

(a) Births to Aboriginal and Torres Strait Islander men, where the mother's Indigenous status was non-Indigenous or not stated, per Aboriginal and Torres Strait Islander man.
(b) Includes Other Territories.


Remoteness Areas

Assumed paternity rates for Remoteness Areas were calculated and adjusted using the same technique as for the states and territories.


Table 8: ASSUMED TOTAL PATERNITY RATES(a), Remoteness Areas

30 June 2017
30 June 2031

Major Cities
1.22
1.40
Inner and Outer Regional
1.09
1.25
Remote and Very Remote
0.24
0.28
Australia(b)
0.94
1.09

(a) Births to Aboriginal and Torres Strait Islander men, where the mother's Indigenous status was non-Indigenous or not stated, per Aboriginal and Torres Strait Islander man.
(b) Includes Other Territories.


MORTALITY ASSUMPTIONS

To produce population projections using the cohort-component method, life tables are required for each year of the projection period. These are calculated in two steps:
  • life expectancy at birth for each projection year is assumed
  • life tables, based on the 2015–2017 age/sex structure of mortality, are generated to match the assumed life expectancies at birth.

Survivorship ratios from the life tables are then applied to the population by single year of age and sex.

Assumptions for mortality at lower geographical levels are based on 2015–2017 differentials between Australia and each state or territory, groups of Indigenous Regions, and Remoteness Areas.


Current life expectancy at birth

At the national level, Aboriginal and Torres Strait Islander life expectancy at birth for the period 2015–2017 is estimated to be 71.6 years for males and 75.6 years for females (see Life Tables for Aboriginal and Torres Strait Islander Australians, 2015–2017 (cat. no. 3302.0.55.003)).

As survivorship ratios are required on a financial year basis, life expectancy at birth estimates are adjusted to account for the six-month period between the midpoint of 2015–2017 (calendar year life expectancy) and 2015–16 (financial year life expectancy), resulting in life expectancy at birth of:
  • 71.4 years for Aboriginal and Torres Strait Islander males
  • 75.5 years for Aboriginal and Torres Strait Islander females.


Trends in life expectancy at birth

The ABS has compiled life tables for Aboriginal and Torres Strait Islander Australians after each Census since 1996. Due to changes in the methods, the 2006, 2011 and 2016 estimates of life expectancy at birth are not comparable to estimates for earlier periods. Assumptions about future levels of Aboriginal and Torres Strait Islander life expectancy at birth can therefore only be based on observed trends over the two most recent intercensal periods.

A study (Wilson, Condon and Barnes, 2007) found evidence that in the Northern Territory:
  • life expectancy at birth increased from 52 years for males and 54 years for females in the 1960's, to 60 years and 68 years respectively in recent years
  • improvements in infant mortality contributed to increases in life expectancy at birth between the late 1960's and early 1980's
  • Since then, life expectancy gains have been largely the result of improving mortality of people aged 45 years and over.

In addition alternative measures indicate some improvement in mortality of Aboriginal and Torres Strait Islander Australians between 1991 and 2005:
  • declines in mortality as measured by age-standardised death rates have been recorded in Western Australia and for females in the Northern Territory
  • declines in infant mortality have been recorded in Western Australia, South Australia and the Northern Territory.

For more information see The Health and Welfare of Australia's Aboriginal and Torres Strait Islander Peoples, Oct 2010, cat. no. 4704.0, Wang Z and Li SQ, 2010, Mortality in the Northern Territory 1967-2006, Health Gains Planning Information Sheet, Dec 2010, Northern Territory Government, Casuarina NT and SCRGSP (Steering Committee for the Review of Government Service Provision) 2011, Overcoming Indigenous Disadvantage: Key Indicators 2011, Productivity Commission, Canberra.


Assumed life expectancy at birth

Three life expectancy at birth assumptions have been used to produce the three main series.

Table 9: LIFE EXPECTANCY AT BIRTH, Assumptions

Assumption
Life expectancy at birth - 30 June 2031
Males
Females
Males
Females

Series A (a)
Annual increase of 0.45 years
Annual increase of 0.35 years
78.2
80.7
Series B (b)
Annual increase of 0.40 years
Annual increase of 0.25 years
77.4
79.2
Series C (c)
Annual increase of 0.25 years
Annual increase of 0.20 years
75.2
78.5

(a) This assumes Aboriginal and Torres Strait Islander population life expectancies will increase at a lower rate than observed in 2011–2016 but at a higher rate than observed in 2006–2016.
(b) This assumes Aboriginal and Torres Strait Islander population life expectancies will increase at the rate observed in 2006-2016.
(c) This assumes Aboriginal and Torres Strait Islander population life expectancies will increase at the rate observed in the total Australian population life expectancies in the last 30 years.

State/territory variations in mortality

Aboriginal and Torres Strait Islander life expectancy at the national level has been calculated using an age-specific adjustment to allow for different patterns in mortality amongst different age groups. This adjustment could not be applied at the state and territory level. For this reason the Australian-level estimates are not strictly comparable with the state/territory level estimates. However, for the purpose of compiling estimates and projections, mortality differentials are calculated based on the relationship of 2015–2017 life expectancies at birth for each state/territory (without age adjustment) compared with Australia (with age adjustment).

Aboriginal and Torres Strait Islander life expectancy at birth differs between the states and territories. For the purposes of these projections, mortality differentials between each state/territory and Australia are calculated and applied to the assumed Australian life expectancies at birth to obtain assumed life expectancy at birth for the states and territories. This method assumes that the mortality differentials, based on those observed during 2015–2017, will remain constant throughout the projection period.

Due to small numbers of deaths registered as Aboriginal and Torres Strait Islander it was not possible to produce Aboriginal and Torres Strait Islander life tables for Victoria, South Australia, Tasmania and the Australian Capital Territory. For the purposes of the projections it is assumed that life expectancy at birth for:
  • Victoria and Tasmania are the same as that for New South Wales
  • South Australia is the same as that for Western Australia
  • The Australian Capital Territory is the same as that derived for the Sydney Indigenous Region.

Table 10: ABORIGINAL AND TORRES STRAIT ISLANDER LIFE EXPECTANCY AT BIRTH AND MORTALITY DIFFERENTIALS(a), State and territories - 2015–2017

Life expectancy at birth
Mortality differentials
Males
Females
Males
Females
years
years
%
%

New South Wales
70.9
75.9
99
100
Queensland
72.0
76.4
101
101
Western Australia
66.9
71.8
93
95
Northern Territory
66.6
69.9
93
92
Australia(b)
71.6
75.6
100
100

(a) Mortality differentials are calculated based on the relationship of 2015–2017 life expectancies at birth for each state/territory (without age adjustment), compared with Australia (with age adjustment).
(b) Includes Other Territories.


Regional variations in mortality

Indigenous regions

To apply assumptions on life expectancy at birth for alternative geographies, Indigenous Regions (IREGs) were aggregated into two groups for each state and territory (except Tasmania and the Australian Capital Territory):
  • capital city IREG (for example, Adelaide IREG)
  • rest of state/territory IREGs combined (for example, Port Augusta IREG and Port Lincoln - Ceduna IREG combined).

To account for under-identification of deaths of Aboriginal and Torres Strait Islander people at smaller geographic level, the number of registered deaths of Aboriginal and Torres Islander people for each IREG group in 2015–2017 was adjusted using state and territory adjustment factors from the 2016–2017 Census and deaths linked data. For more information about the derivation and use of adjustment factors in the compilation of Aboriginal and Torres Strait Islander life tables for the states and territories, see Life Tables for Aboriginal and Torres Strait Islander Australians, 2015–2017 (cat. no. 3302.0.55.003).

A life table methodology was used to obtain life expectancy at birth for 2015–2017 for each IREG group using adjusted deaths in conjunction with 2016 Aboriginal and Torres Strait Islander populations for each IREG group. Differentials were calculated as the ratio of Aboriginal and Torres Strait Islander life expectancy at birth for each IREG group and Australia with age adjustment. This method assumes that under-identification of Aboriginal and Torres Strait Islander deaths is consistent across all regions within each state and territory as information on under-identification is not available at IREG level. Mortality differentials are assumed to remain constant throughout the projection period.


Table 11: ABORIGINAL AND TORRES STRAIT ISLANDER LIFE EXPECTANCY AT BIRTH AND MORTALITY DIFFERENTIALS(a), Indigenous Regions - 2015–2017

Male mortality differentials
Female mortality differentials
Capital city IREG
Rest of state IREG group
Capital city IREG
Rest of state IREG group
%
%
%
%

New South Wales
103
97
102
100
Queensland
105
98
104
99
Western Australia
97
92
98
93
Northern Territory
98
92
97
91
Australia(b)
100
100
100
100

(a) Mortality differentials based on the relationship of 2015–2017 life expectancies at birth for each capital city IREG and rest of state IREG group, compared with Australian life expectancy (with age adjustment).
(b) Includes Other Territories.

As noted above, Aboriginal and Torres Strait Islander life tables were not produced for Victoria, South Australia, Tasmania and the Australian Capital Territory. The following differentials have been used for IREG groups in these states and territories:
  • Victoria: Melbourne IREG uses the Sydney IREG differential, the rest of Victoria IREG uses the rest of New South Wales IREG group differential
  • South Australia: Adelaide IREG uses the Perth IREG differential, and the rest of South Australia IREG group uses the rest of Western Australia IREG group differential
  • Tasmania uses the New South Wales state differential
  • The Australia Capital Territory uses the Sydney IREG differential.


Remoteness areas

Aboriginal and Torres Strait Islander life expectancy at birth differentials for Remoteness Areas were calculated using the same method as that used for IREG groups.


Table 12: ABORIGINAL AND TORRES STRAIT ISLANDER LIFE EXPECTANCY AT BIRTH AND MORTALITY DIFFERENTIALS(a), Remoteness Areas - 2015–2017

Life expectancy at birth
Mortality differentials
Males
years
Females
years
Males
years
Females
years
%
%

Major Cities
72.1
76.5
101
101
Inner and outer Regional
70.0
74.8
98
99
Remote and Very Remote
65.9
69.6
92
92
Australia(b)
71.6
75.6
100
100

(a) Mortality differentials based on the relationship of 2015–2017 life expectancies at birth for each Remoteness Area, compared with Australian life expectancy (with age adjustment).
(b) Includes Other Territories.


INTERSTATE MIGRATION ASSUMPTION

One assumption has been made for future net internal migration of Aboriginal and Torres Strait Islander people:
  • constant levels of migration as observed in the 2016 Census based on address 5 years ago.


Trends in interstate migration

The 'place of usual residence five years ago' Census questions shows that the number of Aboriginal and Torres Strait Islander people who changed their state or territory of usual residence between:
  • 2011 and 2016 was 25,960
  • 2006 and 2011 was 21,340
  • 2001 and 2006 was 18,440.

This measure was unable to account for:
  • Aboriginal and Torres Strait Islander children under five years of age on Census night
  • people whose place of residence five years ago was overseas
  • people whose state or territory of usual residence five years ago was not recorded.

In addition, Aboriginal and Torres Strait Islander people overseas on Census night were not counted in the Census.

Table 13: INTERSTATE ARRIVALS AND DEPARTURES(a)(b) – 2011–2016

State/territory of arrival
State/territory of departure
NSW
Vic.
Qld
SA
WA
Tas.
NT
ACT
Total departures(c)

NSW
. .
1 602
5 390
423
6 64
210
410
706
9 413
Vic.
1 162
. .
958
289
335
191
248
77
3 261
Qld
3 742
1 202
. .
429
1 116
363
1 065
337
8 254
SA
343
332
430
. .
299
47
376
23
1 851
WA
591
382
833
282
. .
168
499
38
2 793
Tas.
220
328
475
62
191
. .
41
18
1 335
NT
462
381
1 405
665
642
79
. .
104
3 736
ACT
629
106
211
11
45
18
36
. .
1 056
Total arrivals (c)
7 166
4 332
9 706
2 166
3 299
1 076
2 674
1 307
31 735
Net movements
-2 247
1 071
1 452
315
506
-259
-1 062
251
. .

. . not applicable
(a) Aboriginal and Torres Strait Islander children under five years of age on Census night were excluded, as were people whose place of usual residence five years ago was overseas or was not recorded.
(b) Data is adjusted to account for Census net undercount and records for which Indigenous status was not stated. See section: Method used to produce interstate migration assumption.
(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, 2016 (cat. no. 2901.0).


Method used to produce interstate migration assumption

State or territory of usual residence on Census night was cross-tabulated with state or territory of usual residence five years ago to obtain net intestate migration for each state and territory for 2011–2016.

These figures are affected by a number of data quality issues, including Census net undercount and records for which Indigenous status was not stated. To account for these, net interstate migration estimates were adjusted by a proportion calculated by dividing Aboriginal and Torres Strait Islander ERP by Aboriginal and Torres Strait Islander Census counts, for each state and territory.

The adjusted net interstate migration estimates were then divided by five to obtain annual movements, which were assumed to remain constant over the projection period. In addition, they were used as constraints on migration assumptions for Indigenous Regions and Remoteness Areas.


Table 14: ASSUMED NET INTERSTATE MIGRATION

NSW
Vic.
Qld
SA
WA
Tas.
NT
ACT
persons
persons
persons
persons
persons
persons
persons
persons
Annual net migration
-452
214
291
62
100
-52
-213
50

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, 2016 (cat. no. 2901.0).


Age/sex profile of interstate migration

The age/sex profile of intestate migration was derived from the 'place of usual residence one year ago' question from the 2016 Census. Arrival and departure rates for the states and territories were calculated by single year of age and sex and adjustments were made where appropriate to ensure the age/sex profiles of projected populations were plausible. All age/sex arrival and departure disaggregations were constrained by the net internal migration assumption at the state/territory level.


Indigenous Regions migration

Annual net migration estimates for each IREG were calculated in the same way as for the states and territories, and were assumed to remain constant over the 15-year projection period.



Table 15: ASSUMED NET INTERNAL MIGRATION, Indigenous Regions

Annual net migration
persons
Dubbo-113
North-Eastern NSW-85
North-Western NSW-142
NSW Central and North Coast236
Riverina - Orange-34
South-Eastern NSW22
Sydney - Wollongong-336
Melbourne136
Victoria exc. Melbourne78
Brisbane606
Cairns - Atherton-44
Cape York-60
Mount Isa-163
Rockhampton-22
Toowoomba - Roma-29
Torres Strait-92
Townsville - Mackay95
Adelaide138
Port Augusta-50
Port Lincoln - Ceduna-26
Broome-7
Geraldton-38
Kalgoorlie21
Kununurra-74
Perth126
South Hedland33
South-Western WA53
West Kimberly-14
Tasmania-52
Alice Springs-5
Apatula-28
Darwin-89
Jabiru - Tiwi62
Katherine-225
Nhulunbuy101
Tennant Creek-29
Australian Capital Territory50



Remoteness Areas migration

Annual net migration estimates for each Remoteness Area were calculated in the same way as for states and territories, and were assumed to remain constant over the 15-year projection period.


Table 16: ASSUMED NET INTERNAL MIGRATION, Remoteness Areas

Annual net migration
persons
Major Cities917
Inner and Outer Regional73
Remote and Very Remote-990



OVERSEAS MIGRATION ASSUMPTION

One assumption has been made for future net overseas migration of Aboriginal and Torres Strait Islander people:
  • zero overseas migration, with zero arrivals and zero departures.


Trends in overseas migration

According to the 2016 Census there were 1,969 Aboriginal and Torres Strait Islander people resident in Australia in 2016 who lived overseas in 2011. Slightly fewer numbers of Aboriginal and Torres Strait Islander people resident in 2011 also lived overseas in 2006 (1375 persons).

This level of in-migration has a negligible effect on the size of the future Aboriginal and Torres Strait Islander population. In addition, there will also be some level of out-migration leading to an even smaller net migration rate.


UNEXPLAINED GROWTH ASSUMPTION

Zero unexplained growth has been assumed for this series of projections.