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INTRODUCTION

1 This publication describes Australia's population growth and distribution, and analyses internal migration dynamics, which is the primary factor that leads to changes in Australia's population distribution. This publication mainly contains final estimated resident population (ERP) data based in the 2001 Census of Population and Housing. Estimates based on previous censuses, particularly 1996, are also included. In some sections, census counts by place of enumeration and place of usual residence have been used.

2 Following the 1992 amendment to the Acts Interpretation Act 1901-1973 to include the Indian Ocean Territories of Christmas Island and Cocos (Keeling) Islands as part of geographic Australia, population estimates at dates commencing from July 1993 include estimates for these two territories. To reflect this change, another category of the state/territory classification was created, known as Other Territories. Other Territories include Jervis Bay Territory, Christmas Island and the Cocos (Keeling) Islands. Prior to July 1993, Jervis Bay Territory was included in estimates for the Australian Capital Territory.

3 In recognition of the inherent inaccuracy involved in population estimation, population figures less than 1,000 in the text are rounded to the nearest ten, figures over 1,000 are rounded to the nearest hundred, and figures over 1 million are rounded to the nearest 100,000. While unrounded figures are provided in the main tables, accuracy to the last digit is not claimed and should not be assumed.


ESTIMATED RESIDENT POPULATION-AUSTRALIA

4 ERP are estimates of the Australian population obtained by adding to the estimated population at the beginning of each period the components of natural increase (on a usual residence basis) and net overseas migration.

5 For the states and territories, account is also taken of estimated interstate movements involving a change of usual residence. 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 agrees with the difference between the ERPs at the two respective census dates.

6 Estimates of the resident population are based on census counts by place of usual residence, with an allowance for net census undercount, to which are added the number of Australian residents estimated to have been temporarily overseas at the time of the census. Overseas visitors in Australia are excluded from this calculation.

7 The concept of ERP links people to a place of usual residence within Australia. Usual residence is that place where each person has lived or intends to live for
six months or more from the reference date for data collection.


ESTIMATION OF SUB-STATE/TERRITORY POPULATIONS

8 In census years the ERP as at 30 June for each Statistical Local Area (SLA) is based on usual residence census counts, with an allowance for net census undercount and the number of residents temporarily overseas at the census date. Overseas visitors in Australia are excluded from this calculation. As the census is held at a date other than 30 June (6 August in both 1991 and 1996, and 7 August in 2001), further adjustments taking into account births, deaths and net migration for the intervening period are made to obtain the ERP at 30 June.

9 For post-censal years, the absence of migration data at the SLA level means that it is not possible to estimate SLA populations by taking into account natural increase and net migration. Instead, ERPs are calculated using a mathematical model. Local knowledge, including that advised by local governments, may be used to adjust the outcome of the model for a particular SLA.

10 In the mathematical model a relationship is established between changes in population and changes in other indicators over the period between the two most recent censuses.

11 The choice of indicators varies across the states and territories, depending on availability, and includes dwelling approvals, electricity connections, Medicare enrolments and drivers' licences. Changes in these indicators are then used to estimate changes in the population of each area since the last Census. The choice of indicators also varies across SLAs depending on aspects such as whether the SLA is urban or rural, is growing or declining, and whether the area has a high or low proportion of houses or medium and high density dwellings.

12 As a result of difficulties in measuring small populations, particularly those of Aboriginal and Torres Strait Islander communities, mathematical models may not been used in calculating post-census year ERPs for these areas. Instead, the ERPs can be derived using a number of indicators including electoral roll enrolments, housing surveys and school enrolments, with account taken of advice provided by Council representatives and area contacts.

13 A more detailed explanation of the concept of ERP, as adopted by the ABS for official population estimates, is contained in Demographic Estimates and Projections: Concepts, Sources and Methods, Statistical Concepts Library, ABS web site.

14 Service population estimates are a different measure of population. They take into account seasonal itinerant populations which are not included in the ERP. Currently the ABS does not produce service population estimates but two working papers are available which investigate the concept and feasibility of such estimates. The working papers are available on the ABS web site by selecting Themes, then Demography, then ABS Demography Working Papers (numbers 96/4 and 99/3).

15 ERPs by census collection districts (CD) were used to calculate the population living within 50 kms of the coast because CDs are the smallest geographical level available. This enabled a more accurate assessment of population within the 50 km zone than SLAs. A 50 km buffer was generated, after thinning the coast to a node separation of 10 km and collinear deviation of 0.1 km (100m). Each CD was assigned a proportion, varying between 0 for a CD outside the buffer and 1 for a CD being completely within the buffer. These proportions were then applied to the CD ERPs to calculate the percentage of the population living within 50 kms of the coast.


INTERCENSAL DISCREPANCY

16 Intercensal discrepancy is the difference between the 2001 Census-based ERP and the 1996 Census-based ERP. The September Quarter 2002 issue of Australian Demographic Statistics (cat. no. 3101.0) included a special article that provided details on the intercensal discrepancy.

17 Intercensal discrepancy for Australia was -0.1% in 2001 after being -0.2% in 1996, 0.3% in 1991, -0.3% in 1986 and 0.3% in 1981. Over this time, intercensal discrepancy has fallen significantly at the state level, with the average absolute error at the state level falling from 1.6% in 1981 to 0.3% in 2001. In 2001, the absolute intercensal error was less than 0.6% for all states and territories, except for the Australian Capital Territory which was 1.6%.

18 The total average growth rate in population includes population change due to natural increase, net overseas migration, interstate migration (for states and territories only) and intercensal discrepancy. However, intercensal discrepancy is not shown in this publication.


CENSUS COUNTS-PLACE OF ENUMERATION

19 The population count for place of enumeration is a count of every person who spent census night in Australia, based on where he or she was counted, including people on board vessels in or between Australian ports, or on long-distance trains, buses or aircraft. People were counted where they spent census night, which may not be where they usually live.


CENSUS COUNTS-PLACE OF USUAL RESIDENCE

20 This is a count of all people within the scope of the Census on the basis of where they usually live, rather than where they were on census night. Each person is required to state his or her address of usual residence in Question 7 (as well as Question 8 and Question 9, where questions were asked about usual residence one and five years ago).


CENSUS COUNTS-INTERNAL MIGRATION

21 Internal migration is the movement of people from one defined area to another within a country. Information on internal migration within Australia is available from the Census.

22 The Census asks a series of questions relating to each person's usual address. The indicative data from these questions are recorded as the Usual Address Indicator Census Night (UAICP), Usual Address One Year Ago Indicator (UAI1P) and Usual Address Five Years Ago Indicator (UAI5P).

23 Data collected in the Census only reflect the latest movement in the intercensal period, even though there may have been multiple movements during this period.

24 Household mobility indicators are also derived using this information. Note that persons temporarily absent, visitors, and households containing only visitors, are excluded from these variables. The following two indicators are available for Census data:

• Household One Year Mobility Indicator (MV1D), where: all residents (aged one year or more) have changed address during the last year; or some residents have changed address during the last year, but all residents stated their address one year ago; or no residents have changed address during the last year; or not stated (including households in which one or more residents did not state his/her usual residence one year ago).
• Household Five Year Mobility Indicator (MV5D), where: all residents (aged 5 years and over) have changed address during the last five years; or some residents have changed address during the last five years, but all residents stated their address of five years ago; or no residents have changed address in the last five years; or not stated (including households in which one or more residents did not state his/her usual residence of five years ago).

	ERP-based	Census counts (a)
	no.	no.
New South Wales	-66,549	-59,718
Victoria	6,444	7,181
Queensland	92,188	82,437
South Australia	-12,894	-10,571
Western Australia	2,886	2,785
Tasmania	-15,043	-13,084
Northern Territory	-2,170	-5,513
Australian Capital Territory	-4,642	-3,156
Australia	. .	. .

• Census Collection Districts (CDs). CDs are designed for use in census years for the collection and dissemination of Population Census data. In non-census years, CDs are undefined. In aggregate, CDs cover the whole of Australia without gaps or overlaps. The CD is the smallest spatial unit in the ASGC. CDs aggregate to form the larger spatial units of SLAs, SSDs, SDs and Local Government Areas, Urban Centres and Localities in the UC/L Structure and Remoteness Areas in the Remoteness Structure. Aggregation of SLAs in turn forms the remaining spatial units in the ASGC. Therefore, in census years, the CD is the common denominator which integrates all classification structures in the ASGC. For the 2001 Census, there were 37,209 CDs were defined throughout Australia.

• Urban Centre/Locality (UC/L). The UC/L structure groups Census Collection Districts (CDs) together to form defined areas according to population size criteria. The resulting areas are known as Urban Centres or Localities. Population counts (place of enumeration) from the latest Census of Population and Housing are used to define the UC/L Structure which means this structure is only current at the time of the Census. In broad terms, an Urban Centre is a population cluster of 1,000 or more people while a Locality is a population cluster of between 200 and 999 people. For statistical purposes, people living in Urban Centres are classified as urban while those in Localities are classified as rural. Each Urban Centre/Locality has a clearly defined boundary and comprises one or more whole CDs.

• Statistical Local Areas (SLAs). These geographical areas are, in most cases, identical with, or have been formed from a division of, whole Local Government Areas (LGAs). In other cases, they represent unincorporated areas. In aggregate, SLAs cover the whole of a state or territory without gaps or overlaps. In some cases legal LGAs overlap statistical subdivision boundaries and therefore comprise two or three SLAs (Part A, Part B and, if necessary, Part C). Australia has 1,353 SLAs.

• Statistical Subdivision (SSDs). These consist of one or more SLAs. In aggregate, they cover the whole of Australia without gaps or overlaps. They are defined as socially and economically homogeneous regions characterised by identifiable links between the inhabitants. In the non-urban areas an SSD is characterised by identifiable links between the economic units within the region, under the unifying influence of one or more major towns or cities. Australia has 207 SSDs.

• Statistical Divisions (SDs). These consist of one or more SSDs. The divisions are designed to be relatively homogeneous regions characterised by identifiable social and economic units within the region, under the unifying influence of one or more major towns or cities. Australia has 66 SDs.

• State and territory. These are the largest spatial units in the ASGC and are political entities with fixed boundaries. Six states and five territories are recognised in the ASGC: New South Wales, Victoria, Queensland, South Australia, Western Australia, Tasmania, Northern Territory, Australian Capital Territory, Jervis Bay Territory and the external territories of Christmas Island and Cocos (Keeling) Islands. Jervis Bay Territory, and the Territories of Christmas Island and Cocos (Keeling) Islands are included as one spatial unit under the category of Other Territories.

• Australian Demographic Statistics, cat. no. 3101.0
• Australian Historical Population Statistics available on AusStats, cat. no. 3105.0.65.001, available on this web site. From the navigation bar select Statistics, then Companion Data; 31.Demography-general
• Australian Standard Geographical Classification (ASGC), 2002, cat. no. 1216.0
• Census of Population and Housing, Data Quality-Undercount, 2001, cat. no. 2940.0
• Population by Age and Sex, Australian States and Territories, cat. no. 3201.0
• Population by Age and Sex, cat. no. 3235.0-8.55.001-state- and territory-specific datasets, available on this web site. From the navigation bar select Statistics, then Data Cubes, then 32. Population trends and estimates.
• Regional Population Growth, Australia and New Zealand, cat. no. 3218.0