INTRODUCTION
1 This publication contains three series of population projections for the Northern Territory by Statistical Division (SD) and major urban areas for the period 1999 to 2021 and by Statistical Subdivision (SSD) and Statistical Local Area (SLA) for the period 1999 to 2011, 2016 and 2021. Population projections by age and sex are also included for the Northern Territory and major urban areas but for selected years from one series only.
2 Additional data relating to this series of projections, including population by sex and single years of age, can be obtained by contacting the ABS Information Service.
OBJECTIVES
3 The Australian Bureau of Statistics (ABS) has published three series of population projections for the Northern Territory and lower geographical levels in the Northern Territory to service the needs of users of population projections.
4 The projection results published by the ABS are not intended as predictions or forecasts, but are illustrations of growth and change in the population which would occur if the assumptions about future demographic trends prevail over the projection period.
5 While the assumptions for the projections are formulated on the basis of an assessment of past demographic trends in the Northern Territory, Australia and overseas, there is no certainty that any of the assumptions will or will not be realised. In addition, no assessment has been made of changes in non-demographic conditions such as major government policy decisions and economic factors which may affect future demographic behaviour.
6 Accordingly, three projection series have been provided in recognition of this uncertainty and to provide users with a range of options.
DEVELOPMENT
7 The process of developing population projections involves research, analysis, consultation and computation. Analysis of demographic trends, research into the determinants of population growth and distribution, and consultation with the Northern Territory Government are necessary to formulate the various assumptions and to ensure their general relevance for the projection period.
8 Consultation with the Northern Territory's Statistical Liaison Committee occurred from June 2000 to February 2001. During this period assumptions initially specified in a Memorandum of Understanding between the ABS and the Statistical Liaison Committee were refined and finalised for three series of population projections. For fertility two alternative assumptions were selected. One assumption was selected for mortality, and three assumptions were selected for both overseas migration and internal migration.
PROJECTION TECHNIQUES
9 There are many techniques which may be used for population projections, ranging from simple extrapolations through to broad economic, social and time-series analysis to detailed component methods. The ABS uses the cohort-component method, which begins with a base population for each sex by single year of age and advances it year by year by applying assumptions regarding future mortality and migration. Assumed age-specific fertility rates are applied to the female populations of child-bearing ages to provide the new cohort of births. This procedure is repeated for each year in the projection period for the Northern Territory. It is repeated to obtain projections by Statistical Division for the Northern Territory, while constraining annually by age and sex to the Northern Territory projections. The technique was also used for population projections at the Statistical Local Area level, with the assumptions taking into account major economic activities that are likely to impact on the population of SLAs in the next 10 years.
ASSUMPTIONS
Fertility
10 Single year age-specific fertility rates for the Northern Territory were calculated by applying the 1996-1998 ratios of the Northern Territory to Australian age-specific fertility to high and low Australian fertility assumptions. The high assumption at the Australian level maintains a total fertility level of 1.75 babies per woman throughout the projection period, while the low assumption assumes fertility declines to 1.60 babies per woman by 2008 then remains constant to the end of the projection period.
11 Age-specific fertility rates for Darwin SD and Northern Territory - Bal SD were calculated by applying fertility differentials for each single year of age to the assumed age-specific fertility rate for the Northern Territory for each year in the projection period. Fertility differentials for Darwin SD and Northern Territory - Bal SD were assumed to be the average differential of the years 1996-1998.
12 Fertility assumptions for SLAs were based on average age-specific fertility rates observed in each SLA between 1995 and 1999, projected to follow the assumed changes at the Northern Territory level until 2008 and then remain constant to 2021.
Mortality
13 Projected life expectancy at birth was based on the Australian trend in life expectancy at birth using five yearly intervals between 1985-1987 and 1995-1997 (centring on the census years). From 1996-1998, male and female life expectancies for Australia were projected to increase by 0.30 and 0.22 years respectively each year until 2002-03; thereafter, life expectancy was assumed to increase at a diminishing rate.
14 The pattern of decline in age-sex-specific death rates from 1970-1972 to 1995-1997 was assumed to continue from 1999 to 2021, within the constraints of the predetermined levels of life expectancy at birth. Where there was an upward trend in age-sex-specific death rates, some limitations were applied to prevent an increase in assumed future mortality rates for particular ages.
15 The mortality assumptions for Darwin SD and Northern Territory - Bal SD were based on the age-sex-specific assumptions for the Northern Territory, adjusted for differences in historical life expectancy. The percentage differentials in life expectancy between Darwin SD and Northern Territory - Bal SD prevailing in 1996-1998 were maintained throughout the projection period.
16 The mortality assumptions for SLAs were based on the age-sex-specific assumed mortality rates for the Northern Territory, adjusted across all ages to provide consistency with the overall mortality experienced in each SLA between 1995 and 1999.
Overseas migration
17 The Northern Territory's average share of Australia's net overseas migration for the three year period 1996-97 to 1998-99 was used as the basis for calculating the share going to the Northern Territory during the projection period.
18 Net overseas migration to the Northern Territory was divided between Darwin SD and Northern Territory - Bal SD based on the proportion of recent arrivals recorded in the 1991 and 1996 Censuses. The average of these two censuses was used to divide net overseas migration into overseas migration by Statistical Division.
19 The assumed age-sex structure of each overseas migration component for the Northern Territory was based on the average structure from 1996-97 to 1998-99. This varies during the projection period because the relative contribution of permanent and long-term components changes as long-term arrivals and departures increase from year to year. Age-sex profiles at the part of Northern Territory level were derived from the 1996 Census question on residence one year ago. Overseas departures are assumed to have much the same age-sex distribution as overseas arrivals. These distributions were constrained to Northern Territory overseas arrivals and departures data for 1995-96. Age-sex profiles for category jumping are assumed to be the same as for permanent arrivals.
Internal migration
20 The long-term average net interstate migration experience of the Northern Territory was used as the basis for the medium assumption for the Northern Territory, with more weight given to the past 10 years. The high and low assumptions reflect the volatility in the Northern Territory's interstate migration data and give a plausible broad range of projection outcomes, particularly in the short term.
21 Net internal migration to Darwin SD and Northern Territory - Bal SD was based on historical trends. Historical net total migration was assumed to be the difference between population growth and natural increase. Net internal migration was assumed to be the difference between net total migration and net overseas migration.
22 Assumed age-sex profiles of future internal flows were derived from the 1996 Census distribution of internal movements in 1995-96, constrained to estimates for interstate migration in 1995-96. Profiles for arrivals and departures were generated separately. Age-sex profiles were assumed to remain unchanged throughout the projection period.
GEOGRAPHIC BOUNDARIES
23 This publication contains data presented according to the geographic boundaries defined in Australian Standard Geographical Classification (ASGC) 2001 (Cat. no. 1216.0).
ACKNOWLEDGMENT
24 ABS publications draw extensively on information provided freely by individuals, businesses, governments and other organisations. Their continued cooperation is very much appreciated: without it, the wide range of statistics published by the ABS would not be available. Information received by the ABS is treated in strict confidence as required by the Census and Statistics Act 1905.
RELATED PUBLICATIONS AND REFERENCES
25 Users may also wish to refer to the following ABS publications:
Australian Demographic Statistics (Cat. no. 3101.0) - issued quarterly
Australian Demographic Trends (Cat. no. 3102.0) - issued irregularly
Births, Australia (Cat. no. 3301.0) - issued annually
Causes of Death, Australia (Cat. no. 3303.0) - issued annually
Deaths, Australia (Cat. no. 3302.0) - issued annually
Demographic Estimates and Projections: Concepts, Sources and Methods, Statistical Concepts Library,
ABS Website - Ausstats
Demography, Northern Territory (Cat. no. 3311.7) - issued annually
Experimental Projections of the Aboriginal and Torres Strait Islander Population (Cat. no. 3231.0) - issued irregularly
Household and Family Projections, Australia, 1996 to 2021 (Cat. no. 3236.0) - issued irregularly
Migration, Australia (Cat. no. 3412.0) - issued annually
Northern Territory at a Glance (Cat. no. 1314.7) - issued annually
Overseas Arrivals and Departures, Australia (Cat. no. 3401.0) - issued monthly
Population by Age and Sex, Australian States and Territories (Cat. no. 3201.0) - issued annually
Population Projections, Australia (Cat. no. 3222.0) - issued irregularly
Population by Age and Sex, Northern Territory (Cat. no. 3235.7) - issued annually
Population by Age and Sex, Northern Territory - Electronic Delivery (Cat. no. 3235.7.55.001) - issued annually
Regional Statistics, Northern Territory (Cat. no. 1362.7) - issued annually
26 Current publications issued by the ABS are listed in the Catalogue of Publications and Products (Cat. no. 1101.0). The ABS also issues, on Tuesdays and Fridays, a Release Advice (Cat. no. 1105.0) which lists publications to be released in the next few days. The Catalogue and Release Advice are available from any ABS office or on the ABS Website.
27 As well as the statistics included in this and related publications, additional information is available from the ABS Website and accessing Themes/Demography.
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