Summary statistics for the three main series of projections (Series A, B and C) are provided in the following data cube:
Projections by age and sex for the three main series for Australia and the states and territories are also available in Time Series Spreadsheet (Microsoft Excel) format.
SUMMARY OF ASSUMPTIONS
Assumptions have been formulated on the basis of demographic trends over the past decade and longer, both in Australia and overseas, in conjunction with consultation with various individuals and government departments 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, catastrophes, wars) which may affect future demographic behaviour.
As future levels of fertility, mortality, overseas migration and internal migration are unpredictable, two or more assumptions have been made for each component. These are intended to illustrate a range of possible future outcomes, although there can be no certainty that any particular outcome will be realised, or that future outcomes will necessarily fall within these ranges.
For the fertility component, assumptions are made about future total fertility rates (TFRs), age-specific fertility rates, and the sex ratio at birth. Three assumptions have been made about Australia's future TFR:
A brief summary of the method used to produce these projections is provided below. For more detailed information, including how assumptions on future fertility, mortality, net overseas migration and net interstate migration were formulated, see Chapter 2—Assumptions of Population Projections, Australia, 2006 to 2101 (cat. no. 3222.0).
The Australian Bureau of Statistics (ABS) uses the cohort-component method for producing population projections. In this method, assumptions made about future levels of fertility, mortality, overseas migration and internal migration are applied to a 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.
The projections span the period 30 June 2008 to 2101 for Australia, and 30 June 2008 to 2056 for the states and territories and capital cities/balance of state.
The base population for all geographic areas is the preliminary estimated resident population at 30 June 2007. Figures for 30 June 2006 are final estimated resident population based on results of the 2006 Census of Population and Housing.
WHICH PROJECTION SERIES TO USE
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 gives a more realistic view of the possible future size, distribution and age structure of Australia's population.
The ABS has produced 54 alternative projection series using different combinations of assumptions on fertility, mortality, overseas migration and interstate migration. The inclusion of a zero net overseas migration assumption increases the total number of available projections to 72.
Different series are appropriate for specific time horizons (shorter or longer term), the region being studied and any volatility in the components. All series can more or less accommodate possible future levels of fertility and mortality as both are fairly predictable. However, there is less certainty of future levels of overseas migration and interstate migration given their historical volatility. This volatility can be expected to continue due to future government policies and decision-making, and economic, social and other determinants and influences, in Australia and overseas.
Projected populations by single year of age and sex for all 72 projection series are provided in the following data cubes:
Under all three scenarios the trend towards older ages of mothers at birth of children is assumed to continue to 2021, but at a slower rate than historical trends, and remain constant thereafter. The sex ratio at birth is assumed to be 105.5 male births per 100 female births for all years.
For the mortality component, assumptions are made about future levels of life expectancy at birth for males and females. Two assumptions have been made:
- high: the TFR will increase to 2.0 babies per woman by 2021, and remain constant thereafter;
- medium: the TFR will decline to 1.8 babies per woman by 2021, and remain constant thereafter; and
- low: the TFR will decline to 1.6 babies per woman by 2021, and remain constant thereafter.
Under both assumptions, the pattern of change in age-sex specific death rates has been assumed to continue until 2026. Thereafter, the age-specific death rates are uniformly scaled to conform to the assumed life expectancy at birth for future years.
Three assumptions have been made about Australia's future levels of net overseas migration (NOM):
- high: life expectancy at birth will reach 93.9 years for males and 96.1 years for females by 2056 and remain constant thereafter. Under this assumption male and female life expectancy at birth will continue to increase by 0.30 and 0.25 years per year respectively until 2056; and
- medium: life expectancy at birth will reach 85.0 years for males and 88.0 years for females by 2056, and remain constant thereafter. Under this assumption life expectancy at birth will increase by 0.25 years for males per year and 0.30 years for females per year until 2011, after which mortality improvement will gradually decline until 2056.
A zero net overseas migration assumption has been included to facilitate analysis of the effect of overseas migration on Australia's future population.
Three assumptions have been made about future net interstate migration levels:
- high: NOM will increase to 220,000 people per year by 2011 and remain constant thereafter;
- medium: NOM will remain constant at 180,000 people per year throughout the projection period; and
- low: NOM will decrease to 140,000 people per year by 2011 and remain constant thereafter.
The medium interstate flows assumptions are based on long-term averages for the states and territories, while the large and small interstate flows assumptions encompass a wider range of values, based on historical variation in levels, to allow for a range of possible future outcomes, especially in the short term.
- large interstate flows: relatively large net interstate migration gains for some states and territories, corresponding to relatively large losses for other states and territories;
- medium interstate flows: medium net interstate migration gains for some states and territories, and medium losses for others; and
- small interstate flows: relatively small net interstate migration gains for some states and territories, and small losses for others.
PROJECTION SERIES, Assumptions used
HIGH LIFE EXPECTANCY AT BIRTH
MEDIUM LIFE EXPECTANCY AT BIRTH
HIGH FERTILITY (TFR = 2.0)
|Net overseas migration (per year)|
MEDIUM FERTILITY (TFR = 1.8)
|Net overseas migration (per year)|
LOW FERTILITY (TFR = 1.6)
|Net overseas migration (per year)|
|(a) The large interstate flows assumption corresponds to large net interstate losses for New South Wales, Victoria and South Australia. For these states, the small interstate flows assumption yields greater population growth.|
NATURE OF PROJECTIONS
The nature of the projection method and inherent fluctuations in population dynamics mean that care should be taken when using and interpreting the projection results. The projections are not forecasts but simply illustrate future changes which would occur if the stated assumptions were to apply over the projection period. The projections do not attempt to allow for non-demographic factors (such as major government policy decisions, economic factors, catastrophes, wars, epidemics or significant health treatment improvements) which may affect future demographic behaviour or outcomes.
It is important to recognise that the projection results given in this report simply reflect the assumptions made about future fertility, mortality and migration trends. While the assumptions are formulated on the basis of an objective assessment of past demographic trends and their likely future dynamics, there can be no certainty that they will be realised.
No liability will be accepted by the Australian Bureau of Statistics for any damages arising from decisions or actions based upon these population projections.
REFERENCING THESE STATISTICS
Source: Australian Bureau of Statistics. Population Projections, Australia, 2006 to 2101 (cat. no. 3222.0).
For further information on population projections refer to the ABS publication Population Projections, Australia, 2006 to 2101 (cat. no. 3222.0). For further information on these and related statistics contact the National Information and Referral Service on 1300 135 070.