People who identified themselves, or were identified by another household member, as being of Aboriginal origin, Torres Strait Islander origin, or both Aboriginal and Torres Strait Islander origin.

See also Aboriginal and Torres Strait Islander ancestries, Indigenous household indicator (INGDWTD), Indigenous status (INGP), Whether reported using an Aboriginal and/or Torres Strait Islander language at home (LNGP) and Aboriginal and Torres Strait Islander family indicator (INGF).

‘A structured label for any location where one would expect to deliver or receive a good or service’. This is the working definition used by Geoscape Australia, which aims to include all physical addresses, and exclude non-physical addresses such as post office boxes or email addresses.

Addresses are collected in the Census because data is required for key characteristics about where Australians live and work. Addresses are collected to:

• release accurate data for geographic areas, such as postal areas, states and territories, capital cities, towns, remote areas and many more
• produce population estimates for regions to help with the distribution of government funds and for electoral purposes
• help understand how and where people travel to work
• enable the development of a higher quality ABS Address Register, which is used widely to develop better survey processes, and improve processes and systems for the next Census.

See also Confidentiality and Name and address retention.

Administrative data is information that government departments, businesses and other organisations collect. They collect information for a range of reasons such as:

• registrations
• sales
• record keeping.

Some examples of administrative data:

• personal income tax information from the Australian Taxation Office
• information about the number of people who use Medicare from the Department of Health.

The ABS only collects and uses administrative data for statistics and research. We don't share or release this information in a way that could identify anyone.

See also how administrative data was used in the Census.

The Census does not seek to separately identify adopted children. An adopted child is, in most cases, reported as the child of person 1 and/or person 2 in the relationship question, and is coded in the same way as a natural child.

See also Child, Child type (CTPP) and Reference person/Person 1.

Australian born includes all people born in Australia, and excludes people:

• born overseas
• born at sea
• whose response was classified 'Inadequately described'
• whose response was classified 'Not elsewhere classified'

Australia in this definition is as set out in section 2B of the Acts Interpretation Act 1901 and for the 2021 Census includes: the six states, the Northern Territory, the Australian Capital Territory, Jervis Bay Territory, and the territories of Christmas Island, Cocos (Keeling) Islands and Norfolk Island.

See also Country of birth of person (BPLP).

ACLD uses data from the Census of Population and Housing to build a longitudinal picture of Australian society. The first release of ACLD was based on a random 5% sample from the 2006 Census, brought together with records from the 2011 and 2016 Census using probabilistic linking methods. 

See also Microdata: Australian Census Longitudinal Dataset.

The Census counts people in Australia on Census Night, therefore Australian residents temporarily overseas are excluded. However, administrative data for overseas arrivals and departures enable their inclusion in the Estimated Resident Population.

See also Estimated Resident Population (ERP) and Temporarily absent. 

Average persons per household (also known as average household size) is the average number of people usually resident in an occupied private dwelling.

This is calculated by taking the sum of the number of persons usually resident in a dwelling for all occupied private dwellings and dividing by the total number of occupied private dwellings. 

The total number of people usually resident in dwellings is calculated from the Number of persons usually resident in dwelling (NPRD). The classification is weighted such that one person receives a weight of one; two people receive a weight of two; and so on until the maximum weight of eight. 

This calculation excludes:

• dwellings where not applicable responses were found in the Number of persons usually resident in dwelling (NPRD) classification and
• visitor only, other non-classifiable and not applicable dwellings using the Household composition (HHCD) classification.

Boarders at school or college are specifically asked to record the address of the school or college as their usual residence if they intend to live there for a total of 6 months or more. This instruction was not given in censuses prior to 1986 and often these people incorrectly reported their family home as their place of usual residence.

See also Type of non-private dwelling (NPDD).

Caravans that are occupied are usually treated as private dwellings. This includes caravans and campervans that are located on: 

• caravan or residential parks
• camping grounds
• roadsides or open land.

Caravans on residential allotments are also usually treated as an occupied private dwelling. The exception to this is where there are one or more other structures on the allotment and the occupants of the caravan are residents of the main dwelling. In this case the occupants are all classed as one household and the caravan is counted as an additional room of the main dwelling. 

See also Dwelling type (DWTD), Dwelling structure (STRD).

The Census and Statistics Act 1905 (CSA) provides the Australian Statistician with the authority to conduct statistical collections, including the Census of Population and Housing, and, when necessary, to direct a person to provide statistical information.

See also Legislative framework and Confidentiality.

The Census counts people where they were located on Census Night and this count of the population is referred to as the place of enumeration count. A count of the population based on their place of usual residence is also available. In censuses prior to 2006, many of the Census products presented data on a place of enumeration basis. Since 2006, the focus has been on place of usual residence.

Census counts by place of usual residence:

• exclude overseas visitors 
• exclude Australian residents temporarily overseas.

The variables Family composition (FMCF) and Household composition (HHCD) are coded on a place of usual residence basis rather than a place of enumeration basis. All visitors to dwellings are excluded when coding these variables. Usual residents who are reported as 'temporarily absent' are included in the coding of Family composition (FMCF) and Household composition (HHCD).

See also Estimated resident population (ERP), Household, Place of enumeration, Place of usual residence (PURP), and Usual residence.

The date of the 2021 Census was Tuesday 10 August 2021.

From the 2001 Census, the Census form has included an optional question asking whether each person in the household agrees to have their personally identified information kept and securely held by the National Archives of Australia for 99 years. This personally-identified Census information will not be available for any purpose (including to courts and tribunals) within the 99 year closed access period and cannot be accessed, altered or retrieved before that time.

After 99 years, the name identified data will be made public for future generations. The first batch of such information, from the 2001 Census, will be publicly available in 2100. Those accessing the information could include genealogists, historians, social analysts and other researchers in the 22nd century.

Unlike other questions, the Census time capsule question on the form does not relate to a specific Census topic and is not listed in the Census Regulations, with other topics. Rather, the Census time capsule was made possible by an amendment to the Census and Statistics Act 1905.

See also Confidentiality and Name and address retention.

This is a person of any age who is a natural, adopted, step, foster or nominal son or daughter of a couple or lone parent, usually resident in the same household. A child is also any individual under 15, usually resident in the household, who forms a parent-child relationship with another member of the household. This includes otherwise related children less than 15 years of age and unrelated children less than 15 years of age.

In order to be classified as a child, the person can have no identified partner or child of their own usually resident in the household. A separate family in the household is formed in this instance. If a person is aged under 15 and has a partner and/or a spouse these relationships are not recorded.

There are three types of children identified by the Relationship in household (RLHP) variable:

• child under 15
• dependent student
• non-dependent child.

Variables relevant to children are:

• Child type (CTPP)
• Count of all children in family (CACF)
• Count of dependent children aged under 15 temporarily absent (CDCAF)
• Count of dependent children in family (CDCF)
• Count of dependent students (15-24 years) temporarily absent (CDSAF)
• Count of non-dependent children in family (CNDCF)
• Count of non-dependent children temporarily absent (CNDAF)
• Count of children with selected long-term health condition(s) in household (CCLTHD)
• Count of dependent children under 15 (CDCUF)
• Count of dependent students (15-24 years) (CDSF)
• Child type (including grandchildren) (CTGP)

Characteristics of children or parents who were temporarily absent on Census Night are not available.

Under the Census and Statistics Act 1905, the personal information you provide in the Census remains strictly confidential to the ABS. The ABS never has and never will release identifiable Census data. Other organisations, including government departments and marketing companies, cannot have access to personal information you provide on your Census form. 

For more information refer to the 2021 Census Privacy Statement.

See also Census time capsule, Introduced random error/perturbation and Name and address retention.

A person who works without pay, in an economic enterprise operated by a relative.

See also Labour force status (LFSP) and Status in employment (SIEMP).

A couple family is identified by the existence of a couple relationship. A couple relationship is defined as two people usually residing in the same household who share a social, economic and emotional bond usually associated with marriage and who consider their relationship to be a marriage or marriage-like union. This relationship is identified by the presence of a registered marriage or de facto marriage. A couple family can be with or without children, and may or may not include other related individuals. A couple family with children present can be expanded to elaborate on the characteristics of those children, such as their number, age and dependency status.

See also Family blending (FBLF), Family composition (FMCF), Marital status, Relationship in household (RLHP) and Same-sex couple.

Data processing includes all steps from receipt of Census responses in either online or in paper form through to the production of a clean Census data file. 

For 2021 Census, a Data Capture Centre (DCC) was established to register, scan and capture data from the paper forms using imaging and Intelligent Character Recognition. A Data Operation Centre was established which was responsible for processing: including frame reconciliation, coding, imputation, editing, and quality assuring all of the 2021 Census Data.

See also 2021 Census methodology and Quality assurance.

Derivation is an automated process where some variables are assigned values based on responses to other questions, or, (where no response has been provided), from other family members present in the same dwelling. Examples of these include deriving age from date of birth or automatically setting fields to not-applicable based on responses to other questions.

See also Imputation and Non-response. 

Destination zones (DZNs) are the spatial unit used to code Place of work (POWP) and are an aggregation of 2021 mesh blocks. DZNs aggregate to statistical areas level 2 (SA2s) in the Australian Statistical Geography Standard (ASGS). Data at DZN level will be available in the Census TableBuilder product.

See also Place of work (POWP) and Australian Statistical Geography Standard (ASGS).

A dwelling is a structure which is intended to have people live in it, and which is habitable on Census Night. Some examples of dwellings are houses, motels, flats, caravans, prisons, tents, humpies and houseboats.

Private dwellings are enumerated using online or paper household forms, which obtain family and relationship data as well as information on the dwelling itself such as rent or mortgage payments and ownership. Non-private dwellings (for example hotels and hospitals) are enumerated using online or paper personal forms. While these forms capture information about the person's residential status within the non-private dwelling, they do not capture information on ownership of, or payments related to, the dwelling.

All occupied dwellings are counted in the Census. Unoccupied private dwellings are also counted. This includes unoccupied units in retirement villages (self-contained). Unoccupied residences of owners, managers or caretakers of caravan parks, marinas and manufactured home estates are also counted, but other unoccupied dwellings in such establishments are not counted.

Since the 2001 Census unoccupied private dwellings have been counted in discrete Indigenous communities.

If a non-private dwelling is unoccupied on Census Night it is out of scope. Unoccupied residences of owners, managers or caretakers of such establishments are counted.

See also Caravans, Dwelling location (DLOD), Dwelling structure (STRD), Dwelling type (DWTD), Household, Manufactured home estates and Type of non-private dwelling (NPDD).

Persons in employment are those of working age who, during a short reference period, were engaged in any activity to produce goods or provide services for pay or profit. Employment is defined as an activity of one hour or more. 

See also Public/private sector (GNGP), Hours worked (HRSP), Labour force status (LFSP), Occupation (OCCP) and Part-time work.

The 'employed away from work' category refers to people who responded that they had a job in the week before the Census, but were away from work on holidays, on paid leave, on strike, or temporarily stood down. It also includes those who stated that they worked in the previous week but did not provide the number of hours worked. Extra guidance was given in the online form for those who weren't working due to COVID-19 restrictions.

See also Labour force status (LFSP).

An employee is a person who works for a public or private employer and receives remuneration in wages or salary; or is paid a retainer fee by their employer, while working on a commission basis; or works for an employer for tips, piece-rates or payment in kind.

See also Public/private sector (GNGP), Hours worked (HRSP), Labour force status (LFSP), Occupation (OCCP) and Status in employment (SIEMP).

Enumeration is the action of counting something. The Census enumerates (or counts) everyone in Australia on Census Night, as well as all the dwellings. 

See also Place of enumeration.

The Estimated Resident Population (ERP) is the official measure of the population of Australia, and is based on the concept of usual residence. It refers to all people, regardless of nationality, citizenship or legal status, who usually live in Australia, with the exception of foreign diplomatic personnel and their families. The ERP includes usual residents who are overseas for less than 12 months and excludes overseas visitors who are in Australia for less than 12 months.

More information on the ERP can be found in the ABS publication National state and territory population, produced quarterly. ERPs for SA2s, LGAs and selected non-ABS structures are published annually in Regional population. More information on demographic publications is available under Population on the ABS website.

See also Australian Statistical Geography Standard (ASGS), Census counts, Place of enumeration, Place of usual residence (PURP).

A number of variables used in the 2021 Census may provide information about ethnic origin. These variables may be cross-classified by sex or other related variables.

See also Ancestry (ANCP), Country of birth of person (BPLP), Country of birth of parents (BPPP), Indigenous status (INGP), Language used at home (LANP), Proficiency in spoken English (ENGLP), Religious affiliation (RELP) and Year of arrival in Australia (YARP).

A family is defined by the ABS as two or more people, 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.

Each separately identified couple relationship, lone parent-child relationship or other blood relationship forms the basis of a family. Some households contain more than one family. Non-related people living in the same household are not counted as family members (unless under 15 years of age).

Other related individuals (brothers, sisters, aunts, uncles) may be present in the household. If more than one family is present these people can only be associated with the primary family.

Visiting families are not included as part of the household, and the relationships of other visitors are not coded. A household containing only a visiting family (e.g. a family at a holiday home) is coded to a household type of visitors only.

Where all people present are aged under 15 years, or where information for each person has been imputed, the household is deemed not classifiable to a family. Of people listed as temporarily absent, only spouse(s) and family children are used in coding family composition.

For further information on families and grandparent families, see Understanding Family composition and Grandparent families. 

Family variables: The basic family classification is Family composition (FMCF). When classifying families, information about temporarily absent family members is used. Other family variables available are:

• Count of all children in family (CACF)
• Count of children aged under 15 temporarily absent (CDCAF)
• Count of dependent children in family (CDCF)
• Count of dependent children under 15 (CDCUF)
• Count of dependent students (15-24 years) (CDSF)
• Count of dependent students (15-24 years) temporarily absent (CDSAF)
• Count of non-dependent children in family (CNDCF)
• Count of non-dependent children temporarily absent (CNDAF)
• Count of persons in family (CPRF)
• Count of persons temporarily absent from family (CPAF)
• Family household composition (HCFMF)
• Grandparent families (FMGF)
• Labour force status of parents/partners in families (LFSF)
• Location of spouse (SPLF)
• Aboriginal and Torres Strait Islander family indicator (INGF)
• Spouse/partner indicator (SPIP)
• Same-sex couple indicator (SSCF)

See also Child, Family blending (FBLF), Family composition (FMCF), Family/household reference person indicator (RPIP) and Relationship in household (RLHP).

First generation Australians are people living in Australia who were born overseas. 

See also Country of birth of person (BPLP) and Understanding migrant statistics in the Census and other data sources.

The term 'foster child' generally refers to a child being raised by an unrelated family in the absence of any natural, adoptive or step parent(s).

In practice, a person is coded to foster child if the response 'foster' is given for that person, regardless of the individual's dependency status.

The variables Child type (CTPP) and Relationship in household (RLHP) have foster child categories.

See also Child and Relationship in household (RLHP).

The Census provides a range of data over different areas and geography levels. The Australian Statistical Geography Standard (ASGS) defines all the geographies used by the ABS for release of data. Each geography has its own name, boundaries, and purpose. 

For more information and definitions on the geographies used in the 2021 Census, see Understanding Census Geography.

See also Special purpose codes.

Government benefits, pensions and allowances are income support payments from government to persons under the social security and related government programs. Included are pensions and allowances received by aged, disabled, unemployed and sick persons, carers, families and children, veterans or their survivors, and study allowances for students. All overseas pensions and benefits are considered income if they are being received when the person completed the Census. Family tax benefit is also regarded as income.

The calculation of total income includes any pensions or benefits received.

See also Total personal income (weekly) (INCP).

The ABS defines a group household as a household consisting of two or more unrelated people where all people are aged 15 years and over. There are no reported couple relationships, parent-child relationships or other blood relationships in these households.

An unrelated child (e.g. boarder) under the age of 15 who lives in a household with one or more usual residents, is coded as forming a parent-child relationship within that household. These households become family households, not group households.

Group households are classified in the variable Household composition (HHCD), and individual members are classified in Relationship in household (RLHP).

See also Child, Family and Household.

Everyone in Australia at Census time needs to be counted in the Census, excluding foreign diplomats and their families, no matter where they may be sleeping on Census Night. To achieve this, the ABS has developed a strategy to obtain the best possible enumeration of people, no matter where they sleep. Some aspects of this strategy include liaising with service providers and engaging specialised field staff to count people sleeping rough on a special interview based form, and providing the ability for people to respond to the usual residence question as 'none' if they have no usual residence. 

See also Estimates of homelessness based on the 2021 Census, Dwelling structure (STRD), Improvised home, Special short form and Usual residence.

The primary imputation method used for the Census is known as 'hotdecking'. Other imputation processes use probability methods. In general the hotdecking method involves locating a donor record and copying the relevant responses to the record requiring imputation. The donor record will have similar characteristics and must also have the required variable(s) stated. In addition the donor record will be located geographically as close as possible to the location of the record to be imputed. The match must occur within the same Capital City or Balance of State.

The methodology for imputation is tailored to two situations. Firstly, where no Census form has been returned and secondly where a partially completed form was returned.

No Census form returned - private dwelling: Where a private dwelling was identified as occupied on Census Night but a Census form was not returned, the number of males and females normally in the dwelling and their key demographic variables require imputation. In these cases, the non-demographic variables are set to 'Not stated' or 'Not applicable'.

For dwellings where the number of males and females is unknown, two imputation processes are performed. Initially, these records have their number of males and females imputed using hotdecking. Then a second imputation (also using hotdecking) is run to impute the key demographic variables for the newly created person records.

To hotdeck the number of males and females, the donor records must meet several conditions:

• they must be occupied private dwellings where a form was returned and contain a maximum of 6 persons
• they must have a similar Dwelling Structure (STRD) and Dwelling Location (DLOD) to the record to be imputed
• they must be located geographically as close as possible to the location of the record to be imputed

The number of males and females are the only data copied from the donor record in the first hotdecking process.

In the next process, the records which have just had their number of males and females imputed, are subjected to the same hotdecking process as those records where the number of males and females had been ascertained.

This hotdecking process imputes the key demographic variables. Again the donor records must meet several conditions:

• they must be records where everyone within the dwelling provided all their demographic characteristics
• they must have similar Dwelling Structure (STRD) and Dwelling Location (DLOD)
• they must have identical counts of males and females and
• they must be located geographically as close as possible to the location of the record to be imputed.

The key demographic variables are then copied from the donor records to the records requiring imputation

No Census form returned - Non private dwelling: Where a person in a non-private dwelling did not return a form, their demographic characteristics are copied from another person in a similar non-private dwelling using Type of non-private dwelling (NPDD).

Census form returned: Where a form was returned, some or all of the demographic characteristics may require imputation. Characteristics are imputed using a combination of hotdecking and probability techniques.

See also Derivation and Imputation.

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

For Census purposes, the total number of households is equal to the total number of occupied private dwellings as a Census form is completed for each household from which dwelling information for the household is obtained.

See also Family, Group household, Household composition (HHCD), Indigenous household indicator (INGDWTD), Lone person household, Relationship between families (FRLF) and Tenure type (TEND).

The Census household form (online or paper) is the primary means for collecting Census data and is used in all private dwellings. The household form records details about the dwelling and characteristics of people in the dwelling. It records details of up to six people on the paper form and up to 25 people on the online form. Extra forms are used if there are more people than this.

To view a PDF version of the Census household form, see Sample copies of the 2021 Census paper forms.

See also Interviewer household form, Personal form, Special short form and Form type (FTCP).

These include sheds, tents, humpies and other improvised dwellings, occupied on Census Night. This category also includes people sleeping rough, such as those sleeping on the streets, in abandoned buildings, under bridges or in cars.  

See also Homelessness enumeration and Dwelling structure (STRD).

Imputation is a statistical process for predicting values where no response was provided to a question and a response could not be derived. In the Census, we impute key demographic variables (sex, age, marital status, and usual residence) where no Census form is returned or when a respondent does not respond to one of these questions.

Where a private dwelling is identified as occupied on Census Night but a Census form has not been returned, people are imputed into that dwelling - both the number of people and their key demographic characteristics.

If a person in a non-private dwelling did not return a form, their demographic characteristics are imputed from people in similar non-private dwellings.

Where a person responds to the Census but does not answer the age, sex, marital status or usual residence questions, values are imputed using other information on the form as well as the distribution of these data items in the responding population. 

Imputation flag variables enable users of Census data to quantify the number of imputed records, for applicable data items, in a given population.

For more information on imputation see the 2021 Census methodology.

See also Derivation, Non-response and Hotdecking.

An Industry refers to individual businesses carrying out similar productive activities that can be grouped together. Individual business entities are assigned to an industry based on the predominant activity identified on the Census form. Industry data is coded to the Australian and New Zealand Standards Industrial Classification (ANZSIC), 2006 (Revision 2.0). 

See also Australian and New Zealand Standards Industrial Classification (ANZSIC), and Industry of employment (INDP). 

2021 Census data was processed using Intelligent Character Recognition (ICR) technology for the paper forms. Specialised computer software is used to interpret the handwriting on images taken of each page of the Census form. Once recognised, answers to Census questions were coded to the appropriate category of the relevant classification, for example Religion, Occupation, etc.

See also Data processing.

Internal migration is the movement of people across a specified boundary within Australia for the purpose of changing their place of usual residence. Information on internal migration within Australia is available from the Census.

The Census asks a series of questions relating to each person's usual address which can be used to identify the change of address of people for one year prior to the Census data, and for five years prior to the Census date. Data collected in the Census only reflect movements which coincide with these particular points in time in the intercensal period (i.e. one year ago and five years ago), even though there may have been multiple movements during this period.

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. 

See also Household one year mobility indicator (MV1D), Household five year mobility indicator (MV5D), Place of usual residence one year ago (PUR1P), Place of usual residence five years ago (PUR5P),  Usual address indicator Census night (UAICP), Usual address one year ago indicator (UAI1P), Usual address five years ago indicator (UAI5P), and Usual residence.

The Interviewer household form is used in Aboriginal and Torres Strait Islander communities (and areas where language differences or other factors make use of the standard self-enumeration forms impractical). The Interviewer household form is an interview based Census form which is used to record the details of up to 12 people in a household, and some dwelling data. If there are more than 12 people in a dwelling, additional Interviewer household forms are used.

To view a PDF version of the Interviewer household form, see Sample copies of the 2021 Census paper forms.

See also Form type (FTCP).

Under the Census and Statistics Act 1905 it is an offence to release any information collected under the Act that is likely to enable identification of any particular individual or organisation. To minimise the risk of identifying individuals in aggregate statistics, a technique has been developed to randomly adjust values. Random adjustment of the data, known as random error or perturbation, is considered to be the most satisfactory technique for avoiding the release of identifiable data while maximising the range of information that can be released. To learn more, see the 2021 Census methodology on Introduced random error/perturbation.  

See also Confidentiality.

The Australian and New Zealand Standard Classification of Occupations (ANZSCO), Version 1.3 defines a job as a set of tasks performed by one individual. An occupation is a collection of jobs that are sufficiently similar in their main tasks to be grouped together for the classification.

See also Australian and New Zealand Standard Classification of Occupations (ANZSCO), Labour force status (LFSP) and Occupation (OCCP).

For Census purposes, the labour force includes people aged 15 years and over who:

• work for payment or profit, or as an unpaid helper in a family business, during the week prior to Census Night
• have a job from which they are on leave or otherwise temporarily absent
• are on strike or stood down temporarily
•  do not have a job but are actively looking for work and available to start work.

The following people are classified as being in the labour force:

• employed people (i.e. the first three groups above)
• unemployed people (i.e. the last group above).

People aged 15 years and over who are neither employed nor unemployed are classified as not in the labour force. This includes people who are retired, pensioners and people engaged solely in home duties (unpaid).

See also and Comparing the 2021 Census and the Labour Force Survey Labour force status (LFSP).

On Census day and the week preceding it, a number of regions across the country were in various stages of lockdown or experiencing other restrictions due to the COVID-19 pandemic. This may have affected the way people responded to the Census form, particularly where there were changes to the person's employment circumstances. Examples of the changes seen in the data included how people travelled to their place of work; how many people worked from home; and a greater number of people being temporarily stood down in the week before the Census. Guidance on how to correctly respond to the relevant questions was provided at the time on the Census website and within the Census online form.

See also the data use consideration sections in the variables in Income and Work and Transport.

Information on how the Census was run during COVID-19 is here. 

A lone parent is a person who has no spouse or partner usually resident in the household, and who forms a parent-child relationship with at least one child usually resident in the household. The child may be either dependent or non-dependent.

See also Relationship in household (RLHP).

A private dwelling, with only one person aged 15 years or over, is classified as a lone person household.

See also Household composition (HHCD). 

Long-term health conditions are diagnosed by a doctor or nurse, last six months or longer and include health conditions that:

• May recur from time to time, or
• Are controlled by medication, or
• Are in remission

See also Comparing ABS long-term health conditions data sources, Long-term health conditions and Type of long-term health condition (LTHP).

Manufactured home estates are land or estates developed specifically for manufactured homes, and on which manufactured homes are installed, or are to be installed.

A manufactured home is a self-contained dwelling that is built off-site and then transported to the estate for installation. This includes any associated structures that form part of the dwelling.

Within the development there must be reticulated water, sewerage, drainage and electricity connected to each lot. There must also be some form of community facilities and transport services available, and reasonable access to medical care, recreational facilities, etc.

This category of the variable Dwelling location (DLOD) specifically excludes all retirement villages.

See also Dwelling, Dwelling location (DLOD) and Dwelling type (DWTD).

There are two variables that may be used to identify a person's marital status: Registered marital status (MSTP) and Social marital status (MDCP).

Registered marital status (MSTP) reports responses to the question 'What is the person's current marital status?' and refers to the legal status of the person, and not necessarily their current living arrangement.

Social marital status (MDCP) reports responses to two questions: 'What is the person's relationship to Person 1/Person 2?' and 'What is the person’s current marital status?'. This variable records a person's relationship status based on their current living arrangements. It identifies whether they form a couple relationship with another person living in the same usual residence, and the nature of that relationship.

See also Registered marital status (MSTP), Social marital status (MDCP) and Relationship in household (RLHP).

Median income is the level of income which divides the units in a group into two equal parts, one half having incomes above the median and the other half having incomes below the median. Medians have been estimated for each income range using data from the Survey of Income and Housing.

For information on how medians are used in the derivation of Total personal income (weekly) (INCP).

See also Household income derivation indicator (HIDD),Total family income (weekly) (FINF), Total household income (weekly) (HIND) and Total personal income (weekly) (INCP).

Mnemonics are a shorthand method of describing Census variables when specifying output requirements. Each variable relates to either a dwelling (or household), family or person. The last character of the mnemonic (D, F or P) indicates the unit to which the classification relates. For example, AGEP is the mnemonic for the person level variable, Age. The default order of the variable index in this dictionary is alphabetic order by mnemonic.

For the 2021 Census, a maximum of three families can be identified in one household. In cases where more than three families are identified in a household, the first three families are coded and other persons are classified as either related family members of the primary family or non-family members.

Relevant variables are Family composition (FMCF), Family number (FNOF) and Relationship between families (FRLF).

See also Family and Household.

The collection of names and addresses in the Census is a critical part of ensuring the quality and value of the Census.

Names are collected in the Census for many reasons, including: 

• Making it easier for the person completing the form to provide the right information for each person in the household
• Enabling high quality data linking for important research for projects, such as enabling more accurate estimation of Aboriginal and Torres Strait Islander life expectancy: Indigenous Mortality Project
• Enabling the Post Census Review (also known as the post enumeration survey) to assess the quality of Census data. The Post Census Review is a short survey run in the month after the Census to determine how many people were missed or counted more than once, and to independently assess completeness of the Census.

Following a consultation process and Privacy Impact Assessment the ABS made the decision to retain names for up to 18 months and addresses for up to 36 months. The names will be used to generate anonymised keys that can be used to combine existing data sets to create richer and more valuable statistics for Australians.

See also Confidentiality, Name and address retention and Census time capsule.

After the Census has been conducted and forms have been processed, the ABS will separate names and addresses from other information on the Census form (e.g. age, sex, occupation, level of education or income). The names and addresses are then stored securely and separately from other Census data and no one is ever able to view your name or address with your other Census data. This practice is known as the Separation Principle. 

The ABS will retain names for up to 18 months and addresses for up to 36 months.

See also Address, Census time capsule, Confidentiality and Name.

For each employed person, their employer's business name and address is requested on the Census form. This information is used to assist in classifying the employed person's Industry of employment (INDP).

See also Australian and New Zealand Standard Industrial Classification (ANZSIC), Confidentiality, Industry of employment (INDP) and Industry.

Negative income occurs when the operating expenses are higher than the gross receipts (or revenue) of a self-employed person, business or a rental property. A person has negative income if these losses are greater than any income, benefits or allowances received from other sources.

See also Total personal income (weekly) (INCP).

A nominal child is any individual under 15 years of age who does not have a parent usually resident in the household but is instead assigned to a nominal parent from among other household members. Such children may be related to the nominal parent (e.g. as a nephew or niece) or not be related at all. Allocation of a nominal parent to a nominal child is determined by the application of certain coding rules. For more information refer to the Family, household and income variables, 2014.

See also Child and Family composition (FMCF).

Non-binary sex was the third response category to the sex question in the 2021 Census. The inclusion of this third category was to allow respondents to participate in the Census when the male and female sex categories did not accurately describe their sex.

See also Non-binary sex in the 2021 Census and Analysis of non-binary sex responses.

A person for whom there is no identified couple relationship, parent-child relationship, or other blood relationship with any of the other usual residents of the household. They may live within a family household, or they may form a non-family household either as a lone person or a group household.

A non-family member is a person who is either:

• a lone person
• a group household member or
• an unrelated individual living in a family household.

See also Dwelling, Household, Relationship in household (RLHP), Visitors to a household and Visitors to Australia.

Non-response refers to the situation where a response to one or more questions (items) on the form was not answered.

Item non-response occurs:

• where a household or person returns a form but does not answer one or more questions
• where a household or person does not respond to the Census at all.

For the key demographic variables (sex, age, marital status and usual residence) we impute values where non-response occurs. The corresponding imputation flags for these variables indicate if the item was imputed.

Where non-responding persons have been imputed, the remaining questions are either set to 'item non-response' or 'not applicable', depending on the imputed age of the person.

For detailed information on non-response, see 2021 Census methodology.

See also Derivation and Imputation.

Persons not in the labour force are those people who, during the week prior to Census Night, were neither employed nor unemployed. They include people who were performing unpaid home duties, caring for children, retired, voluntarily inactive, permanently unable to work, in jail, trainee teachers, members of contemplative religious orders, and people whose only activity during the week prior to Census Night was jury service or unpaid voluntary work for a charitable organisation.

See also Labour force and Labour force status (LFSP).

A one-parent family consists of a lone parent with at least one child (regardless of age) who is also usually resident in the household and who has no identified partner or child of their own. The family may also include any number of other related individuals.

Examples of one parent families include: a 25-year-old parent with dependent children; and an 80-year-old living with a 50-year-old child.

Information on people who are temporarily absent is used in family coding to differentiate between lone person households and one parent families (if child was temporarily absent) or between one parent and couple families (if a spouse was temporarily absent).

See also Child, Family, Lone parent, Relationship in household (RLHP) and Temporarily absent.

The term "or equivalent" can include:

• other terms used to describe years of schooling in Australia, which may have changed over time, as well as school level education undertaken at other institutions (e.g. TAFE)
• Year 12 equivalents can include: year 13, 6th form, Higher School Certificate and matriculation
• Year 10 equivalents can include: 4th form
• overseas qualifications comparable to Australian levels of schooling, for example the German Abitur is equivalent to year 12 in Australia

The International Baccalaureate is equivalent to year 12 in Australia.

Certificate level qualifications (e.g. Certificate I-IV) attained while studying at school are non-school qualifications and are not equivalent to school level qualifications (e.g. Year 12).

For information about how school and non-school qualifications are treated when determining highest educational attainment, see Level of highest educational attainment (HEAP).

Other family is defined as a group of related individuals residing in the same household, who cannot be categorised as belonging to a couple or one parent family.

If two brothers, for example, are living together and neither is a spouse or partner, a lone parent or a child, then they are classified as an other family. However, if the two brothers share the household with the daughter of one of the brothers and her husband, then both brothers are classified as other related individuals and are attached to the couple family.

See also Couple family, Family, Family composition (FMCF), One-parent family and Other related individual.

An individual who is related to at least one other member of the household, but who does not form an identified couple relationship or parent-child relationship according to the priority rules of family coding. They can be related through blood, step or in-law relationship and include any direct ancestor or descendant. Relatives beyond first cousin are excluded.

Other related individuals are attached to an existing family nucleus formed by a couple relationship or parent-child relationship. If no such nucleus exists but individuals in a household are related to each other (see list below) they form an 'Other family' in the Family composition (FMCF) classification.

The Relationship in household (RLHP) variable is used to identify other related individuals. The following is a list of relationships used to define an other related individual:
son in-law, daughter in-law, grandmother, step grandmother, grandmother in-law, grandfather, step grandfather, grandfather in-law, granddaughter, step granddaughter, granddaughter in-law, grandson, step grandson, grandson in-law, sister, step sister, half-sister, sister in-law, brother, step brother, half brother, brother in-law, aunt, step aunt, aunt in-law, uncle, step uncle, uncle in-law, nephew, step nephew, nephew in-law, niece, step niece, niece in-law, cousin, step cousin, cousin in-law.

See also Family, Other family, Family composition (FMCF) and Relationship in household (RLHP).

An overcount is when a person was counted more than once, or in error in the Census.

Some reasons why people may have been overcounted include:

• they were included on the Census form at the dwelling where they usually live, even though they stayed and were counted elsewhere on Census Night
• they have multiple usual residences
• they moved during the Census period and completed forms at both their previous and new address
• they were overseas on Census Night and were included on a Census form.

See also Undercount and/or underenumeration, 2021 Census overcount and undercount and Post Census Review (PCR).

For the 2021 Census, people are classified as overseas born if:

• they were born in a country other than Australia
• they were born at sea
• their response was classified 'Inadequately described'
• their response was classified 'Not elsewhere classified'.

Australia in this definition is as set out in section 2B of the Acts Interpretation Act 1901, and for the 2021 Census includes the states and territories and the other territories of Christmas Island, Cocos (Keeling) Islands, Jervis Bay Territory and Norfolk Island. It excludes the other Australian external territories (Australian Antarctic Territory, Heard and McDonald Islands, Ashmore and Cartier Islands and the Coral Sea Territory).

See also Country of birth of person (BPLP) and Understanding Migrant statistics in the Census and other data sources.

An owner manager is a person who works in their own business, with or without employees, whether or not the business is of limited liability.

See also Labour force status (LFSP), Status in employment (SIEMP) and Number of employees (EMPP).

A parent is a natural, adoptive, step, foster mother or father of a child, or a person who is assigned as a nominal parent. This person must be usually resident in the same household as the child.

See also Child, Family, Family composition (FMCF), Nominal child and Relationship in household (RLHP).

The existence of a parent-child relationship is one of the foundations on which separate families and particular family composition categories are identified. It only refers to relationships between people usually resident in the same household. It includes relationships in which people actually report a parent-child relationship on the Census form (including being an adopted child or a foster child of an adult), as well as some designated relationships (i.e. for children aged less than 15 years who do not otherwise have a parent in the household, in which case a nominal parent/child relationship is established).

An individual may be both a parent and a child of other people in the household. For example, a person could live with their father or mother and have a child of their own. If a child in a household is also identified as being a parent, then precedence is given to the person's role as a parent for family composition coding purposes.

See also Child, Family, Family composition (FMCF), Number of children ever born (TISP) and Parent.

A person identified as being in a couple relationship with another person usually resident in the same household is a partner. The couple relationship is established through reporting of either a registered or de facto marriage and includes same-sex couples.

See also Marital status and Same-sex couple.

A person is considered to be working part-time if they worked less than 35 hours in all jobs during the week prior to Census night. This is consistent with the definition of employed part-time in the Labour Force, Australia publication.

See also Labour force status (LFSP) and Hours worked (HRSP).

The Census personal form (online or paper) records details for one person only. It contains the same questions as the Census household form but excludes the questions related to the dwelling. It is used for people staying in a non-private dwelling such as a hotel, motel, hostel, or nursing home. It may also be used when a private dwelling requests an additional form (e.g. large households or if an individual wants to keep their responses private) and the household has already completed a household form.

To view a PDF version of the Census personal form, see Sample copies of the 2021 Census paper forms.

See also Household form and Form type (FTCP).

The place of enumeration is the place at which the person is counted on Census Night, which may not be where they usually live.

The population count for place of enumeration is a count of every person, who spends Census Night in Australia, based on where the person is counted. It includes people on board vessels in or between Australian ports, or on long-distance trains, buses, or aircraft. This count is also known as a de facto population count.

People entering Australia from overseas before midnight on Census Night are counted where they stayed on Census Night. Visitors to Australia are counted regardless of how long they have been in the country or how long they plan to stay. Australian residents in Antarctica are also within the scope of the Census.

People leaving an Australian port for an overseas destination before midnight on Census Night are not counted in the Census. Australian residents out of the country on Census Night, and overseas diplomatic personnel and their families in Australia are out of the scope of the Census.

This type of count provides a snapshot of the population 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.

See also Comparing Place of enumeration with Place of usual residence and Place of usual residence (PURP).

Since the 1966 Census, each Census has been followed by a Post Census Review Survey (PCR), conducted by specially trained interviewers. This is also known as a Post Enumeration Survey (PES). A sample of over 40,000 private dwellings is collected in the survey from all states and territories.

The main purpose of the PCR is to measure the extent of undercount and overcount in the Census. This is achieved by asking respondents where they were on Census night, and whether they were or might have been included on a Census form. At each of these addresses, their personal information is matched to any corresponding Census forms for these addresses to determine whether a person was counted, was counted more than once, or was not counted at all.

Results obtained in the PCR are used to adjust Census counts in the calculation of Estimated Resident Population (ERP) figures for Australia. The results also provide an assessment of the coverage of the Census and are used to inform improvements for future censuses.

See also Estimated Resident Population (ERP) and Undercount and/or underenumeration.

The Post Enumeration Survey (PES), also known as the Post Census Review Survey (PCR), is a measure of the extent of undercount and overcount in the Census.

For more information, see Post Census Review (PCR).

See also Estimated Resident Population (ERP) and Undercount and/or underenumeration.

Quality assurance is a measure to ensure that the Census data is fit for purpose and that the data is not misleading. The ABS has a Data quality framework which ensures that the data is relevant, released in a timely manner, accurate, coherent, accessible, and easy to interpret. The Quality declaration details how the Census addresses each of these elements. 
 
See also 2021 Census Statistical Independent Assurance Panel, Data processing, Managing Census Quality.

If the tables available in standard Census products do not meet a user's needs, then user defined customised tables can be created. Customised tables often require the use of recodes, tailored to the user's requirements. Recodes re-group fields in a classification. More complex user defined fields are new fields that can be created based on conditions applied to existing fields. User defined fields can be created from two or more fields in a database or can consist of mathematical functions.

A recode example:

Standard Labour force status classification
1 Employed, worked full-time
2 Employed, worked part-time
3 Employed, away from work
4 Unemployed, looking for full-time work
5 Unemployed, looking for part-time work
6 Not in the labour force
& Not stated
@ Not applicable
V Overseas visitor

Recoded Labour Force Classification

1 Employed
2 Unemployed
3 Not in the labour force
& Not stated

Explanation:
The recoded Labour Force Classification was recoded by:

• Grouping all employed persons (codes 1, 2 and 3) to be one item called Employed
• Grouping unemployed persons (codes 4 and 5) to be one item called Unemployed
• Including Not in the labour force (code 6) and Not stated (code &) as single items
• Excluding Not applicable and Overseas visitors from the recode.

This recode can now be used with other standard or recoded classifications.

A User Defined Field example:

• Selecting Registered Nurse from the Occupation classification 
• Creating a recode for age by grouping ages 25-40.

These two selections can be combined using a User Defined Field function and labelling this as 'Registered Nurses aged 25-40 years'. This could then be used in creating a variety of tables about this group.

A reference person is usually Person 1 on the Census form and forms the basis of a statistical family. Other household members are linked to the reference person to build the relationships within the household. Sometimes we need to allocate the reference person to a different household member to preserve the data quality of the relationship or family. 

The reference person must be:

• at least 15 years of age
• a usual resident of the household
• at home on Census Night.

See also Understanding Family composition and Grandparent families.

Dwellings, people, and item response rates are internationally recognised measures that indicate the quality of Census data. Response rates give an overall indication of the number of responses to the Census, while item response rates are an indicator of a response to specific questions. For more information on response rates and item response, please see Census form and Understanding data quality. 

The dwelling response rate measures the number of private dwellings that returned a completed Census form, as a proportion of all private dwellings believed to be occupied on Census Night. 

The person response rate measures how many people are included on a returned Census form as a proportion of all people (responding and non-responding) in Australia on Census Night.
 
See also 2021 Census methodology.

Two persons of the same sex who report a de facto or married partnership in the relationship question, and who are usually resident in the same household, are a same-sex couple.

See also Marital status, Relationship as reported for couples (RLCP) and Relationship in household (RLHP).

Second generation Australians are Australian-born people living in Australia, with at least one parent born overseas. 

See also Country of birth of person (BPLP), Country of birth of parents (BPPP), Understanding Migrant statistics in the Census and other data sources and Understanding and using Ancestry data.

Self-enumeration is the term used to describe the way Census data is collected. The Census forms are generally completed by householders (or individuals in non-private dwellings) rather than by interviewers, although interviewers are available in some areas.

Socio-Economic Indexes for Areas (SEIFA) is an ABS product that ranks areas in Australia according to relative socio-economic advantage and disadvantage. The indexes are based on information from the Census.

SEIFA consists of four indexes: the Index of Relative Socio-economic Disadvantage (IRSD); the Index of Relative Socio-economic Advantage and Disadvantage (IRSAD); the Index of Education and Occupation (IEO); the Index of Economic Resources (IER).

Each index is a summary of a different subset of Census variables and focuses on a different aspect of socio-economic advantage and disadvantage.

Special purpose codes allow address data to be coded to a non-spatial value. This occurs where there is insufficient information to code to a physical geographic area. For example, responses with no fixed address or instances of incomplete location information.

Special purpose codes have been created for each hierarchical level within the Australian Statistical Geography Standard (ASGS) Main Structure. These codes are not spatial. They do not have a region associated with them in the various ASGS digital boundary sets.

In the Main Structure, special purpose codes relate to States/Territories, SA4s, SA3s, SA2s and SA1s. They are also included in other ASGS areas such as Greater Capital City Statistical Area (GCCSA) and in Non-ABS structures.

For more information, refer to the Australian Statistical Geography Standard (ASGS).

The Special short form is used in most areas of Australia to enumerate people who are sleeping rough. It is in paper format only and field staff use it to interview this population group. It records details for one person only and contains a small subset (10) of the same questions as the Census household form.

To view a PDF version of the Special Short form, see Sample copies of the 2021 Census paper forms.

See also, Homelessness enumeration, Household form and Improvised home.

In a couple family, a step child is a child who is either the natural child of one partner but not of the other, or who was reported as being the step child of both parents. As a consequence of relationship breakdown or the death of a spouse, some one parent families may also have children reported as step children.

In practice, a person is considered a step child if the response 'step' is given for that person, regardless of the individual's dependency status.

See also Child, Child type (CTPP) and Relationship in household (RLHP).

Most variables in the Census Dictionary have supplementary codes and categories. We use supplementary codes to code responses that do not fit into the main categories.

They include:

• Not stated
• Not applicable
• Overseas visitor
• Inadequately described
• So described
• Not further defined (nfd)
• Not elsewhere classified (nec)

For further explanation of the supplementary codes, see Understanding supplementary codes in Census variables.

The Census form seeks information about people who usually reside in a dwelling but who are temporarily absent on Census Night. Coders use the following temporary absentees in determining household and family classifications:

• partners
• children
• co-tenants or unrelated flatmates (used to classify group households).

The only information gathered on temporarily absent persons are name, sex, age, Aboriginal and/or Torres Strait Islander origin, person's relationship in household and whether the person is a full-time student. This information is used to assist in family coding. 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 this dwelling.

See also Child, Household, Partner and Persons temporarily absent.

Third-plus generation Australians are Australian-born people whose parents were both born in Australia. One or more of their grandparents may have been born overseas or they may have several generations of ancestors born in Australia. 

See also Country of birth of person (BPLP), Country of birth of parents (BPPP), Understanding Migrant statistics in the Census and other data sources and Understanding and using Ancestry data.

Although extensive efforts are made to contact all occupied dwellings and count all unoccupied private dwellings in the Census, locating and contacting them all is not possible. Some dwellings may not be identified. For example, flats above or behind shops or attached to private dwellings may not be included in the Census. Analysis of the undercount in previous censuses has shown that people away from their usual residence on Census Night (for example, travelling, camping, staying in a non-private dwelling, or visiting friends) are more likely to be missed than people at home on Census Night.

Even when a household is contacted, undercount is possible if not all members of the household can be included on the form (six people can be recorded on the paper form and 25 on the online form), and no extra online or paper forms are obtained. Undercount is also possible if the household, or a member of the household, fails to complete a Census form.

A measure of the extent of underenumeration is obtained from the Post Census Review (PCR) (also known as the Post Enumeration Survey (PES)). The official population estimates produced by the ABS take into account the results of the PCR. However, the Census counts are not adjusted.

See also 2021 Census overcount and undercount, Estimated Resident Population (ERP) and Post Census Review (PCR).

Unemployed persons are defined as all those of working age who:

• were not in employment
• carried out activities to seek employment during a specified recent period
• were currently available to take up employment given a job opportunity.

The unit record file (URF) is a sequence of records held on computer files. It holds coded data for all the person, family and dwelling characteristics in each Statistical area level 1 (SA1) as collected in the Census. It is the original source of all Census products. It excludes records for persons listed as temporarily absent, as their details will have been recorded at their place of enumeration on Census Night (if they were not overseas).

Census data are stored in a hierarchy of records for each dwelling. Each dwelling may contain a number of family records. Each of these, in turn, may contain a number of person records. When using household or family data it is necessary to recognise these three levels and understand the concepts at each level.

The three levels are indicated by the last character in the mnemonic for each variable. Dwelling level variables are indicated by D, family level by F, and person level by P.

The URF is held under strict security and is only accessible by certain ABS officers.

See also Data processing and Mnemonics.

A person who lives in a family household, but who is not related to any person in any of the families in the household.

See also Relationship in household (RLHP).

Usual residence data provides information on the usually resident population of an area, and on the internal migration patterns at the state and regional levels. The 2021 Census has three questions on usual residence that ask where the person usually lives on Census Night, and where the person usually lived one year ago and five years ago. Usual address information is used to code usual residence. Population measures based on place of usual residence are also referred to as the de jure population.

See also Comparing Place of enumeration with Place of Usual Residence, Place of usual residence (PURP), Usual address indicator Census night (UAICP), Temporarily absent and Visitors to a household.

A visitor to a household is anyone who does not usually live in the household in which they were enumerated on Census Night. Characteristics of individual visitors to a household are available at the household of enumeration.

The relationship of visitors to one another, or to any resident (including cases where all the people enumerated are visitors) is not further classified.

Households containing only visitors are excluded from family variables, and the internal migration variables.

See also Family, Household, Internal migration, Place of enumeration and Usual residence.

The question on the Census form, 'Where does the person usually live?' allows the identification of people who are usually resident in another country. These overseas visitors are identified as a separate category (coded as V) for all applicable variables.

For the 2006, 2011, 2016 and 2021 censuses, overseas visitors were those people who indicated they would be usually resident in Australia for less than a 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.

See also Place of enumeration and Place of usual residence (PURP).

The working population consists of all people who were employed in the week prior to Census night.

See also Labour force status (LFSP).