EXPLANATORY NOTES
INTRODUCTION
1 This publication contains revised estimates of the resident populations (ERP) by age and sex, of Australian states and territories, as at 30 June 2004 and preliminary estimates as at 30 June 2005. Mean ages and sex ratios for the states, territories and Australia are also included. These data are based on the 2001 Census of Population and Housing.
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 Territories, while not detailed separately, are included in tables where specifically noted.
RESIDENT POPULATION ESTIMATES SERIES
3 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, Statistical Concepts (cat.no. 3228.0).
METHOD OF ESTIMATION
4 The estimates by age of the population of Australia and the states and territories at the date of the census are derived from the census counts by place of usual residence, by adjusting for under-enumeration and adding the number of Australian residents estimated to have been temporarily overseas at the time of the census.
5 Post-censal population estimates are obtained by advancing the previous year's estimates to the next year by subtracting deaths and adding births and net estimated interstate and overseas migration. After each census, estimates for the preceding intercensal period are revised by incorporating an additional adjustment (intercensal discrepancy) to ensure that the total intercensal increase at each age agrees with the difference between the estimated resident populations at the two respective census dates.
Net overseas migration
6 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 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. 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, from the publication Australian Demographic Statistics (cat. no. 3101.0).
Net interstate migration
7 Estimates of interstate migration since June 1986 have been derived from the latest census data on interstate movement in the preceding one year and five years, 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. Medicare Australia now performs all the functions and provides all the services that were performed by the Health Insurance Commission (HIC).
AVERAGE ANNUAL RATE OF GROWTH
8 The average annual growth rate, r, is calculated as a percentage using the formula:
where P0 is the population at the start of the period, Pn is the population at the end of the period and n is the length of the period between Pn and P0 in years.
ACCURACY/RELIABILITY
9 It should be noted that while the Australian Bureau of Statistics (ABS) seeks to produce the most accurate estimates of the population possible, the accuracy of the estimates depends on the quality of the source data used. The major source of potential error is considered to be the estimates of interstate migration based on Medicare transfer data.
10 Single year age estimates are not shown for persons aged 85 years or older. The reliability of age estimates decreases as older ages are reached. However, estimates for each age up to 99 and 100 years or more have been calculated and are available on request.
11 In recognition of the inherent accuracy involved in population estimation, population figures over 1,000 in the text are rounded to the nearest hundred, and figures less than 1,000 are rounded to the nearest ten. While unrounded figures are provided in tables, accuracy to the last digit is not claimed and should not be assumed.
ACKNOWLEDGMENT
12 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 in 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 PRODUCTS
13 Previous issues of this series containing consolidated data were issued on 23 August 1982 (containing estimates for the years 1977 to 1982); 8 December 1987 (containing estimates for the years 1981 to 1987); 21 July 1993 (containing estimates for the years 1992 to 1997); 27 March 2003 (containing estimates for the years 1997 to 2002). Time series spreadsheets of these data for each state and territory and Australia from June 1971 to June 2005 are available for free from the ABS web site, or on AusStats and ABS@ Products and Information then time series spreadsheets under cat. no. 3201.0.
14 Other ABS products which may be of interest to users include:
AusStats - electronic data <https://www.abs.gov.au/ausstats> (see Explanatory Note 15).
Australian Demographic Statistics (cat. no. 3101.0) - issued quarterly
Australian Demographic Trends (cat. no. 3102.0) - issued irregularly
Australian Historical Population Statistics (cat. no. 3105.0.65.001)
Births, Australia (cat. no. 3301.0) - issued annually
Deaths, Australia (cat. no. 3302.0) - issued annually
Demographic Estimates and Projections: Concepts, Sources and Methods, Statistical Concepts (cat.no. 3228.0)
Migration, Australia (cat. no. 3412.0) - issued annually
Overseas Arrivals and Departures, Australia (cat. no. 3401.0) - issued monthly
Population Projections, Australia (cat. no. 3222.0) - issued every two to three years
Regional Population Growth, Australia (cat. no. 3218.0) - issued annually
ADDITIONAL STATISTICS AVAILABLE
15 As well as the statistics included in this and related publications, the ABS may have other relevant data available on request. Inquiries should be made to the National Information and Referral Service on 1300 135 070 or by visiting the ABS web site at <https://www.abs.gov.au>
16 AusStats is a web based information service which provides ABS full standard product range online. It also includes companion data in multidimensional datasets in SuperTABLE format, and time series spreadsheets.
17 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 <https://www.abs.gov.au>. The ABS also issues a daily Release Advice on the web site which details products to be released in the week ahead.
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