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EXPLANATORY NOTES


INTRODUCTION

1 This quarterly publication contains the most recent estimates of the resident populations (ERP) of Australia and the states and territories based on the results of the Census of Population and Housing held on 7 August 2001 (with various adjustments described in paragraph 4). The publication contains the latest available statistics on births, deaths (including infant deaths) and overseas and interstate migration. In addition, the publication includes estimates of the resident population by age groups, major population regions and experimental estimates and projections of the Aboriginal and Torres Strait Islander population. It also includes projected resident populations, projected number of households and projected average household size. Periodically, articles on specific demographic topics will be released on the ABS web site in conjunction with this publication.

2 Following the 1992 amendments to the Acts Interpretation Act to include the Indian Ocean Territories of Christmas Island and the Cocos (Keeling) Islands as part of geographic Australia, population estimates commencing from September quarter 1993 include estimates for these two territories. To reflect this change, another category of the state and territory level has been created, known as Other Territories. Other Territories include Jervis Bay Territory, previously included with the Australian Capital Territory, as well as Christmas Island and the Cocos (Keeling) Islands, previously excluded from population estimates for Australia. Data for Other and External Territories are detailed separately in table 7.

3 Estimates for Australian External Territories will be updated annually as at 30 June unless a more recent estimate is required for electoral apportionment purposes under the Commonwealth Electoral Act 1918.

POPULATION AND COMPONENTS OF POPULATION CHANGE

4 Australia’s population estimates for the period since 1971 are compiled according to the place of usual residence of the population. An explanation of the place of usual residence conceptual basis for population estimates is given in Demographic Estimates and Projections: Concepts, Sources and Methods (cat. no. 3228.0).

Method of estimation

5 The estimated resident population is an estimate of the Australian population obtained by adding to the estimated population at the beginning of each period the component of natural increase (on a usual residence basis) and the component of net overseas migration. For the states and territories, account is also taken of estimated interstate movements involving a change of usual residence. Estimates of the resident population are based on census counts by place of usual residence, to which are added the estimated net census undercount and Australian residents estimated to have been temporarily overseas at the time of the census. Overseas visitors in Australia are excluded from this calculation.

6 After each census (at 30 June of the census year), estimates for the preceding intercensal period are revised by incorporating an additional adjustment (intercensal discrepancy) to ensure that the total intercensal increase agrees with the difference between the estimated resident populations at the two 30 June dates in the respective census years.

Natural increase: births and deaths

7 Natural increase is a major component of ABS quarterly state and territory population estimates and is calculated using the estimated number of births and deaths. The births and deaths data in this release are shown by state and territory of usual residence, using year/quarter of registration for preliminary data and year/quarter of occurrence for both revised and final data. This may affect time series comparisons within relevant tables. For preliminary estimates, births and deaths by quarter of registration are used as a proxy for quarter of occurrence. For revised estimates, a factor has been applied to the number of occurrences to allow for those occurrences which were yet to be registered at the time of revision. For final estimates between 30 June 1991 and 30 June 2001, year/quarter of occurrence data are used. For further details see Demography Working Paper 1998/2 - Quarterly Birth and Death Estimates (cat. no. 3114.0).

8 The timeliness and accuracy of ABS quarterly population estimates depends in part on the timeliness and accuracy of estimates of births and deaths which are based on registrations. To be able to provide timely estimates the ABS produces preliminary estimates using births and deaths by quarter of registration as a proxy for quarter of occurrence. The major difficulty in this area stems from the fact that while the vast majority of births and deaths are registered promptly, a small proportion of registrations are delayed for months or even years. Lags or accumulations in births and deaths registrations can be caused by either:

• late notification of a birth or death event to a state or territory registry;
• delays arising from incomplete information supplied for a registration;
• procedural changes affecting the processing cycles in any of the state and territory registries; and
• resolution of issues that may arise within the ABS or registry processing systems.

Net overseas migration

10 Conceptually, net overseas migration (NOM) is the difference between permanent and long-term arrivals, and permanent and long-term departures. Estimates of NOM are derived from information provided on incoming and outgoing passenger cards, as well as other data supplied by the Department of Immigration and Citizenship (DIAC), formerly the Department of Immigration and Multicultural Affairs (DIMA) and the Department of Immigration and Multicultural and Indigenous Affairs (DIMIA). Data on the intended duration of stay of overseas visitors arriving in Australia and the intended duration of absence of Australian residents travelling overseas are used to determine the numbers of permanent and long-term arrivals, and permanent and long-term departures. Passenger card data are also used to calculate migration adjustments and determine the state and territory distribution of NOM. The processes of adjusting movement data on travellers' stated intentions to reflect their actual behaviour are complex, and depend upon the amount and type of movement data available at a particular point in time. The methods currently used compare data on actual travel movements over a one year period with those first advised by individual travellers, and are explained in more detail in Demography Working Paper 2003/5 - Net Overseas Migration: Adjusting for Actual Duration of Stay or Absence (cat. no. 3137.0). In order to conduct such a comparison, data for a 15 month period (i.e. one year plus one quarter) are required.

11 The adjustment methods described in the working paper have been applied to NOM data from the September quarter 2001 onwards and will be subject to further investigation and improvement with the accumulation of additional data and time series. For more information see the Technical Note - Measuring Net Overseas Migration.

Net interstate migration

12 Estimates of interstate migration since June 1986 have been derived from the latest census data on interstate movement in the preceding one year and unidentified information on interstate changes of address advised to Medicare Australia in the process of administering Medicare. Medicare Australia came into operation on 1 October 2005, and now performs all the functions and provides all the services that were previously administered by the Health Insurance Commission. For further information on the process of estimating interstate migration and the administrative data used, see the Demography Working Paper: 2004/1 Review of Interstate Migration Method (cat. no. 3106.0.55.001) and the Information Paper: Evaluation of Administrative Data Sources for Use in Quarterly Estimation of Interstate Migration, 2006 to 2011 (cat. no. 3127.0.55.001).

Defence force adjustment

13 Medicare theoretically covers all Australian usual residents as well as those non-Australian residents granted temporary registration. However, there are a range of Australian usual residents who do not access the Medicare system, primarily due to access to alternative health services. One group is the military. As such, estimates of interstate migration produced from the interstate migration model described in the working paper Demography Working Paper: 2004/1 Review of Interstate Migration Method (cat. no. 3106.0.55.001) are adjusted to compensate for defence force movements not covered by Medicare. These adjustments are estimated using counts of defence force personnel by age, sex and state/territory, obtained from the Department of Defence, with 70% of any change in quarterly defence numbers assumed to be due to interstate migration not otherwise covered by the model.

CORRECTION OF PRISON DATA FOR QUEENSLAND

14 For the 2001 Census of Population and Housing, most prison data was received for processing via electronic data files. During the post-processing evaluation cycle, it was established that the male and female counts for Queensland prisons (only) were incorrectly captured. This resulted in the publication of incorrect census counts for males and females for various Queensland geographical areas and, as a consequence the incorrect numbers for males and females for Queensland and Australia. Revised population estimates for the 2001-02 financial year phased in a correction for this error. Information on the geographical areas affected are available in the 2001 Census Working Paper-Fact Sheet: Correction of Prison Data for Queensland (cat. no. 2970.0.55.026).

RATES OF POPULATION GROWTH

15 The average annual growth rate, r, is calculated as a percentage using the formula

r =

where P₀ is the population at the start of the period, P_n is the population at the end of the period and n is the length of the period between P_n and P₀ in years.

EXPERIMENTAL ESTIMATES OF ABORIGINAL AND TORRES STRAIT ISLANDER POPULATION

16 Estimates of the Indigenous population are experimental in that the standard approach to population estimation is not possible because satisfactory data on births, deaths and internal migration are not generally available. Furthermore, there is significant intercensal volatility in census counts of the Indigenous population, thus adding to the problem of estimating the true Indigenous population. This volatility can in part be attributed to changes to the Indigenous population that can not be attributed to natural increase or interstate migration. As a result, a method based on the use of life tables is used to produce time series data. For further details see Experimental Estimates and Projections, Aboriginal and Torres Strait Islander Australians (cat. no. 3238.0).

EXPERIMENTAL PROJECTIONS OF ABORIGINAL AND TORRES STRAIT ISLANDER POPULATION

17 Experimental estimates of the Indigenous population as at 30 June 2001 are used as the base population for projections of the Indigenous population to 30 June 2009. A low and a high projection series have been generated, and respectively imply a low and high overall growth rate of the Indigenous population. The low series assumes a change to the Indigenous population is a result of natural increase and, for states and territories, a result of interstate migration. The high series assumes an increase in the Indigenous population observed between the 1996 and 2001 censuses which cannot be attributed to natural increase. For further details see Experimental Estimates and Projections, Aboriginal and Torres Strait Islander Australians, 1991-2009 (cat. no. 3238.0).

OVERSEAS ARRIVALS AND DEPARTURES ESTIMATION METHOD

18 Overseas arrival and departure statistics are derived from a combination of full enumeration and sampling. All permanent movements and all movements with a duration of stay of one year or more are fully enumerated and processed. All movements with a duration of stay of less than one year are sampled. Statistics relating to these movements are therefore estimates which may differ from statistics which would have been obtained if details of all these movements had been processed.

19 From July 1998 DIAC has been able to determine the actual length of stay for departing overseas visitors and arriving Australian residents previously collected from information on intended length of stay supplied on the arrival or departure card by the passenger. This new method has resulted in a change in data distribution with the number of passengers staying for one year exactly declining significantly.

POPULATION PROJECTIONS

20 Population projections presented in this publication are not predictions or forecasts. They are an assessment of what would happen to Australia's population if the assumed levels of components of population change - births, deaths and migration - were to hold for the next 50-100 years.

21 The ERP at June 2004 is the base for the projections series. The three series presented in this publication, and their assumptions are as follows:

• Series A (high series) - assumes the TFR will reach 1.9 babies per woman by 2018 and then remain constant, life expectancy at birth will continue to increase until 2050-51 (reaching 92.7 years for males and 95.1 years for females), NOM will reach 140,000 by 2007-08 and then remain constant, and high flows of interstate migration.
• Series B (medium series) - assumes the TFR will decrease to 1.7 babies per woman by 2018 and then remain constant, life expectancy at birth will continue to increase each year until 2050-51, though at a declining rate (reaching 84.9 years for males and 88.0 years for females), NOM will be held constant at 110,000 per year throughout the projection period, and medium flows of interstate migration.
• Series C (low series) - assumes the TFR will decrease to 1.5 babies per woman by 2018 and then remain constant, life expectancy at birth will continue to increase each year until 2050-51, though at a declining rate (reaching 84.9 years for males and 88.0 years for females), NOM will reach 80,000 per year by 2007-08 and then remain constant, and low flows of interstate migration.
  For additional series and information (e.g. age, sex, states/territories and capital cities/balances of state) see Population Projections, Australia, 2004-2101 (cat. no. 3222.0).

23 Data presented in tables 17 and 18 are not intended as predictions or forecasts, but are illustrations of growth and change in the numbers of households and average household size which would occur if the assumptions about future trends in living arrangements were to prevail over the projection period. For more information see Household and Family Projections, Australia, 2001 to 2026 (cat. no. 3236.0).

ROUNDING

24 In this publication population estimates and their components have sometimes been rounded. Rounded figures and unrounded figures should not be assumed to be accurate to the last digit shown. Where figures have been rounded, discrepancies may occur between sums of component items and totals.

RELATED PRODUCTS

25 Other ABS products which may be of interest to users include:

• Australian Demographic Trends (cat. no. 3102.0)
• Australian Historical Population Statistics (cat. no. 3105.0.65.001)
• Births, Australia (cat. no. 3301.0)
• Causes of Death, Australia (cat. no. 3303.0)
• Deaths, Australia (cat. no. 3302.0)
• Demographic Estimates and Projections: Concepts, Sources and Methods (cat. no. 3228.0)
• Divorces, Australia (cat. no. 3307.0.55.001)
• Experimental Estimates and Projections, Aboriginal and Torres Strait Islander Australians, 1991 to 2009 (cat. no. 3238.0)
• Household and Family Estimates, Australia, June 2001 (cat. no. 3236.0.55.001)
• Household and Family Projections, Australia, 2001 to 2026 (cat. no. 3236.0)
• Household and Family Projections, Australia: Projected Households (cat. no. 3236.0.55.002)
• Household and Family Projections, Australia: Projected Families (cat. no. 3236.0.55.003)
• Household and Family Projections, Australia: Projected Persons by Living Arrangements (cat. no. 3236.0.55.004)
• Household Estimates, Australia (cat. no. 3229.0)
• Information Paper: Census of Population and Housing, Data Quality - Undercount, Australia, 2001 (cat. no. 2940.0)
• Measuring net undercount in the 2006 Population Census, 2006 (cat. no. 2940.0.55.001)
• Information Paper: Determining Seats in the House of Representatives - Legislative Requirements for Provision of ABS Statistics (cat. no. 3107.0.55.002)
• Information Paper: Improved Methods for Estimating Net Overseas Migration (cat. no. 3107.0.55.003)
• Information Paper: Statistical Implications of Improved Methods for Estimating Net Overseas Migration, Australia 2006 (cat. no. 3107.0.55.005)
• Marriages, Australia (cat. no. 3306.0.55.001) - includes data on the marital status of the ERP of Australia
• Migration, Australia (cat. no. 3412.0) - includes data on the country of birth of the ERP of Australia
• Overseas Arrivals and Departures, Australia (cat. no. 3401.0) - issued monthly
• Population by Age and Sex: Australian States and Territories (cat. no. 3201.0)
  • For sub state population data at SLA or LGA geographic levels, refer to the following suite of electronic publications:
  • Population by Age and Sex, Australia (cat. no. 3235.0.55.001)
  • Population by Age and Sex, New South Wales (cat. no. 3235.1.55.001)
  • Population by Age and Sex, Victoria (cat. no. 3235.2.55.001)
  • Population by Age and Sex, Queensland (cat. no. 3235.3.55.001)
  • Population by Age and Sex, South Australia (cat. no. 3235.4.55.001)
  • Population by Age and Sex, Western Australia (cat. no. 3235.5.55.001)
  • Population by Age and Sex, Tasmania (cat. no. 3235.6.55.001)
  • Population by Age and Sex, Northern Territory (cat. no. 3235.7.55.001)
  • Population by Age and Sex, Australian Capital Territory
    (cat. no. 3235.8.55.001)
• Population Projections, Australia (cat. no. 3222.0)
• Regional Population Growth, Australia (cat. no. 3218.0)

27 Current publications and other products released by the ABS are listed in the Catalogue of Publications and Products (cat. no. 1101.0). The Catalogue is available from any ABS office or the ABS web site. The ABS also issues a daily Release Advice on the web site which details products to be released in the week ahead.

28 Statistics of overseas arrivals and departures and related data are also published regularly by DIAC (see the Department’s quarterly publication, Immigration Update) and by the Tourism Research Australia (on international travel and tourism).