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EXPLANATORY NOTES


INTRODUCTION

1 This publication contains final rebased estimates of the resident populations (ERP) by age and sex, of Australian states and territories, as at 30 June 2006, resbased estimates as at 30 June 2007 and preliminary estimates 30 June 2008 onwards. Mean ages and sex ratios for the states, territories and Australia are also included. These data are based on the 2006 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 Population Estimates: Concepts, Sources and Methods (cat. no. 3228.0.55.001).


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.


AVERAGE ANNUAL RATE OF GROWTH

6 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, 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.


ACCURACY/RELIABILITY

7 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.

8 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 are available in the time series spreadsheets released with this publication.

9 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

10 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

11 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 2009 are available for free from the ABS web site in time series spreadsheets under cat. no. 3201.0.

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

• Animated population pyramids for Australia and each state and territory are available on the ABS website <www.abs.gov.au> by selecting Australia's Population and scroll to Animated Population Pyramids.
• Australian Demographic Statistics (cat. no. 3101.0) - issued quarterly
• Australian Demographic Trends (cat. no. 3102.0)
• Australian Historical Population Statistics (cat. no. 3105.0.65.001)
• Births, Australia (cat. no. 3301.0) - issued annually
• Census of Population and Housing - Details of Undercount, Aug 2006 (cat. no. 2940.0)
• Census of Population and Housing - Undercount (cat. no. 2940.0)
• Deaths, Australia (cat. no. 3302.0) - issued annually
• Population Estimated: Concepts, Sources and Methods (cat.no. 3228.0.55.001)
• 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: Measuring Net Undercount in the 2006 Population Census, 2007 (cat. no. 2940.0.55.001)
• Information Paper: Statistical Implications of Improved Methods for Estimating Net Overseas Migration, Australia 2007 (cat. no. 3107.0.55.005)
• Migration, Australia (cat. no. 3412.0) - issued annually
• Population by Age and Sex, Regions of Australia (cat. no. 3235.0)
• 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.