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INTRODUCTION

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).


METHOD

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:

• Projected population, Australia, 2006–2101—in SuperTABLE format
• Projected population, capital city/balance of state, 2006–2056—in SuperTABLE format for each state/territory

• Projected population, components of change and summary statistics, 2006–2101—in Microsoft Excel format for Australia, state/territory and capital city/balance of state

• 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.

• 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.

• 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.

• 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.

	HIGH LIFE EXPECTANCY AT BIRTH				MEDIUM LIFE EXPECTANCY AT BIRTH
	Net interstate migration (large flows)(a)	Net interstate migration (medium flows)	Net interstate migration (small flows)(a)		Net interstate migration (large flows)(a)	Net interstate migration (medium flows)	Net interstate migration (small flows)(a)
HIGH FERTILITY (TFR = 2.0)
Net overseas migration (per year)
220,000	1(A)	2	3		4	5	6
180,000	19	20	21		22	23	24
140,000	37	38	39		40	41	42
0	55	56	57		58	59	60
MEDIUM FERTILITY (TFR = 1.8)
Net overseas migration (per year)
220,000	7	8	9		10	11	12
180,000	25	26	27		28	29(B)	30
140,000	43	44	45		46	47	48
0	61	62	63		64	65	66
LOW FERTILITY (TFR = 1.6)
Net overseas migration (per year)
220,000	13	14	15		16	17	18
180,000	31	32	33		34	35	36
140,000	49	50	51		52	53	54(C)
0	67	68	69		70	71	72
(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.