PROJECTIONS

Summary of assumptions

Assumptions have been formulated on the basis of past demographic trends, in conjunction with consultation with various experts and government department representatives 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, epidemics or significant health treatment improvements) which may affect future demographic behaviour or outcomes.

Three assumptions are made about fertility rates of Aboriginal and Torres Strait Islander women:

• constant fertility rates;
• an annual decline of 0.5% in fertility rates; and
• an annual decline of 1.0% in fertility rates.

Three paternity assumptions, that is the proportion of births born to an Aboriginal and Torres Strait Islander father and mother whose Indigenous status is non-Indigenous or not stated, were also made:

• constant paternity rates;
• an annual increase of 1.0% in paternity rates; and
• an annual increase of 2.0% in paternity rates.

Three assumptions were made about future Aboriginal and Torres Strait Islander life expectancy at birth for Australia:

• Aboriginal and Torres Strait Islander life expectancy at birth will increase by 0.2 years per year for males and 0.15 years per year for females, reaching 72.0 years for males and 75.9 years for females by 2026. This equates to an increase in life expectancy at birth of 3 years over the 15 year projection period for males and 2.25 years for females;
• Aboriginal and Torres Strait Islander life expectancy at birth will increase by 0.3 years per year for males and 0.25 years per year for females, reaching 73.5 years for males and 77.4 years for females by 2026. This equates to an increase in life expectancy at birth of 4.5 years over the 15 year projection period for males and 3.75 years for females; and
• Aboriginal and Torres Strait Islander life expectancy at birth will increase by 0.5 years per year for males and 0.45 years per year for females, reaching 76.5 years for males and 80.4 years for females by 2026. This equates to an increase in life expectancy at birth of 7.5 years over the 15 year projection period for males and 6.75 years for females.

As data are required on a financial year basis, life expectancy at birth estimates were adjusted to account for the six-month period between the midpoint of 2010-2012 (calendar year life expectancy) and 2010-11 (financial year life expectancy). This results in life expectancy at birth of 69.0 years and 73.6 years for Aboriginal and Torres Strait Islander males and females respectively for Australia for the year ending 30 June 2011, which forms the starting point of the life expectancy at birth assumptions.

Additional assumptions regarding the remaining demographic factors for the projections will be:

• constant interstate migration at levels observed in the 2011 Census;
• zero net overseas migration with no arrivals and no departures; and
• zero unexplained growth in the Aboriginal and Torres Strait Islander population.

Projection series

By considering likely scenarios of future levels of fertility, paternity, mortality, migration and using a zero assumption for unexplained growth, 10 projection series were produced.

Three main series have been selected from these to provide a range, although not the full range, of projections for analysis and discussion in Chapters 1 and 3. These series are referred to as series A, B and C. These series are identified as high, medium and low. Detailed information on these and the remaining projection series are available in the data cubes for this release on the ABS web site.

2.1 PROJECTION SERIES (A-J), Assumptions used(a)
		Life expectancy at birth
		1(b)	2(c)	3(d)
CONSTANT PATERNITY RATES
Fertility rates
	Constant	J	. .	. .
	Annual decrease of 0.5%	. .	F	. .
	Annual decrease of 1%	C	. .	. .
1% ANNUAL INCREASE IN PATERNITY RATES
Fertility rates
	Constant	. .	D	. .
	Annual decrease of 0.5%	I	B	H
	Annual decrease of 1%	. .	E	. .
2% ANNUAL INCREASE IN PATERNITY RATES
Fertility rates
	Constant	. .	. .	A
	Annual decrease of 0.5%	. .	G	. .
	Annual decrease of 1%	. .	. .	. .
. . not applicable
(a) Levels of interstate migration as observed in the 2011 Census and zero net overseas migration apply to all series.
(b) Aboriginal and Torres Strait Islander life expectancy at birth increases by 0.2 years per year for males and 0.15 years per year for females, reaching 72.0 years for males and 75.9 years for females by 2026.
(c) Aboriginal and Torres Strait Islander life expectancy at birth increases by 0.3 years per year for males and 0.25 years per year for females, reaching 73.5 years for males and 77.4 years for females by 2026.
(d) Aboriginal and Torres Strait Islander life expectancy at birth increases by 0.5 years per year for males and 0.45 years per year for females, reaching 76.5 years for males and 80.4 years for females by 2026.

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 Australian Bureau of Statistics will be using Series B in calculating fertility and mortality rates for inclusion in the annual Births and Deaths publications.

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 than 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 2011 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 of this release on the ABS web site.

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