Australia's population can be measured in several ways:
  • Census counts by place of enumeration
  • Census counts by place of usual residence
  • estimated resident population.

In addition, the Census provides counts of:
  • the working population
  • families and households.

Census counts - Place of Enumeration

The Census count for Place of Enumeration is a count of every person in Australia on Census Night, based on where they were located on that night. This may or may not be the place where they usually live.

It includes:
  • people on board vessels in or between Australian ports, or on long-distance trains, buses or aircraft
  • people entering Australia from overseas before midnight on Census Night
  • Australian residents in Antarctica.

It excludes:
  • people leaving an Australian port for an overseas destination before midnight on Census Night
  • Australian residents who were out of the country on Census Night
  • overseas diplomatic personnel and their families in Australia.

Visitors to Australia are counted regardless of how long they have been in the country or how long they plan to stay. In the 1996 Census, overseas visitors were those people who indicated they would be usually resident in Australia for less than six months. Since the 2001 Census, overseas visitors have been those people who indicated they would be usually resident in Australia for less than one year.

Since the 1996 Census, overseas visitors have been separately categorised in standard tabulations, with the exception of Age (AGEP), Sex (SEXP) and Registered Marital Status (MSTP) tabulations. Overseas visitors can be identified for AGEP, SEXP, and MSTP by cross-classifying with a variable which contains a separate overseas visitor category.

The Census count by place of enumeration provides a snapshot in any given area. Although the Census is timed to attempt to capture the typical situation, holiday resort areas, such as the Gold Coast and snow fields, may show a large enumeration count compared with the usual residence count.

Census counts based on place of enumeration can be provided for individual Statistical Areas Level 1 (SA1s), and any aggregations of SA1s, such as Postal Areas (POAs) or Statistical Areas Level 2 (SA2s).

Census counts - Place of Usual Residence

The Census count for Place of Usual Residence (PURP) is a count of every person in Australia on Census Night, based on the area in which they usually live. Each person is required to state their address of usual residence in Question 8 on the Census form. Where sufficient information is provided, this enables the area in which they usually live to be identified and coded. The count of persons at their usual residence is known as the de jure population count.

Census counts compiled on this basis minimise the effects of seasonal factors such as the school holidays and snow season, and provide information about the usual residents of an area as well as internal migration patterns at the state/territory and regional levels.

Prior to 2001, Place of Usual Residence was only coded to SLA level. For the 2001 and 2006 Census, usual residence data were available at Collection District (CD) level. For the 2006 Census, if respondents gave insufficient usual address information, their usual residence was imputed at CD level, whereas in 2001, it was classified as 'Inadequately described'.

With the introduction of the Australian Statistical Geography Standard (ASGS) for the 2011 Census, usual residence data are available for Statistical Area Level 1 (SA1) and can be aggregated to higher levels of geography such as Postal Areas (POAs) and State Suburbs (SSCs). However it is only coded if sufficient information is supplied and, if respondents give insufficient usual address information, their usual residence will be imputed at SA1 level. The variable Imputation Flag for Place of Usual Residence (IFPURP) is used to indicate if a person's place of usual residence has been imputed for the Census.

The 2011 Census also asks where a person usually lived one year ago and five years ago. Data for these questions are coded to the Statistical Area Level 2 (SA2). Use of usual residence indicators, in conjunction with the other variables relating to usual residence, makes it possible to identify the pattern of net movement of people between three dates, i.e. Census Night, one year ago and five years ago.

Census usual residence counts form the basis of the Estimated Resident Population (ERP).

Estimated Resident Population

The Estimated Resident Population (ERP) is the official ABS estimate of the Australian population. Among its many uses are the determination of the number of representatives from each state and territory to sit in the House of Representatives, and the annual allocation of Commonwealth funds for state governments and local government. The ERP is based on Census of Population and Housing usual residence counts. It is compiled as at 30 June of each Census year and updated quarterly between Censuses. These intercensal estimates of the resident population are revised each time a population Census is conducted.

In compiling 30 June ERP for a Census year, three important factors are taken into account:
  • Census net underenumeration (or undercount). The level of underenumeration is derived from the Census Post Enumeration Survey (PES) which is conducted soon after the Census, and from estimates based on demographic analysis.
  • Australian residents who are temporarily overseas on Census Night and are therefore not covered by the Australian Census. The number of such people is obtained from statistics on overseas arrivals and departures.
  • The Census does not fall on 30 June. For example, the 2011 Census was held on 9 August. Back-dating of population estimates from 9 August to 30 June is accomplished using data from birth and death registrations, overseas arrivals and departures, and estimates of interstate migration, for the period 1 July to 9 August.

For more information, see Population Estimates: Concepts, Sources and Methods, 2009 (cat. no. 3228.0.55.001).

The working population

The working population consists of all persons who were employed in the week prior to Census Night. It is not possible to distinguish between workers working standard hours and shift workers, as the data collected relate to all workers.

Place of Work data provide information about where working Australians are employed at the time of the Census. Place of work data are only applicable to persons aged 15 years and over.

The working population can be used to calculate daytime populations for an area. These are particularly relevant in commercial and industrial areas. These data, when combined with statistics on how people get to work and on the availability of cars, are used to plan for roads and public transport. They are also used in planning for the location of services, since many services need to be located where people will be during the day, rather than where they live.

The address of the person's workplace in the week prior to Census Night is coded to a Destination Zone (DZN) using an index provided by the State Transport Authorities. Destination Zones do not concord with Statistical Areas Level 1 (SA1s) but they do aggregate to Statistical Areas Level 2 (SA2s), and it is at the SA2 level that Place of Work data can be used in conjunction with other aggregated Census data. For the 2011 Census, destination zones also aggregate to the Statistical Local Area (SLA) level.

The Working Population Profile shows the characteristics of the working population in an SA2. Customised tables of Place of Work data can be obtained through the ABS Information Consultancy Service; they can be specified as flow tables of journey to work data containing both origin (place of enumeration or place of usual residence) and destination (place of work) data.

Journey to work data are used by transport authorities, associated bodies, organisations and other interested people to plan public transport systems, and for the development and release of residential and commercial land.

Place of Work data have been produced from Australian Censuses since 1971. Because of changes and growth in the urban areas of states and territories, destination zones are not necessarily the same each Census.

Journey to work origin and destination data can be cross classified with Method of Travel to Work (MTWP) to identify urban transport patterns. However, users should be aware of the difference in the time period covered by these variables. People employed in the week prior to the Census, but no longer employed on Census Day, still appear in Place of Work data.

Families and households

Family and household data from the Census are based on persons usually resident. When coding the variables Family Composition (FMCF) and Household Composition (HHCD), information about usual residents temporarily absent is taken into account and visitors to the household are disregarded.

Age, sex, student status and relationship information are collected for persons temporarily absent, as this is sufficient for family and household coding purposes. All other information for persons temporarily absent, and in Australia on Census Night, should have been obtained at their place of enumeration. However, this information is not able to be related back to their place of usual residence.

Coders use the following temporary absentees in determining household and family classifications:
  • partners
  • children
  • co-tenants or unrelated flatmates (used to classify group households).

Note that family and household structures are not coded for dwellings where all occupants are absent on Census Night, for example, on holidays. The dwelling would be classified as unoccupied and the holidaying family would be coded as a visitor-only household at the holiday home.

The ABS defines a family as two or more persons, one of whom is at least 15 years of age, who are related by blood, marriage (registered or de facto), adoption, step or fostering, and who are usually resident in the same household.

A household is defined as one or more persons, at least one of whom is at least 15 years of age, usually resident in the same private dwelling.

If more than three families are found in a household, only three families are separately classified and any other people are classified as either related family members or non-family members as appropriate.

The variable Family Household Composition (HCFMF) is new for the 2011 Census and is derived from the Family Composition (FMCF) and Household Composition (HHCD) variables. It counts the types of families within family households. It counts all family types in multiple family households.

For more information, please refer to the 2011 Census Dictionary (cat. no. 2901.0).