Underlying concepts

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Family, Household and Income Unit Variables
Reference period

Name of variable

The name of the variable is 'Family composition'.

Nominal definition

The variable 'Family composition' is nominally defined as: 

  • The composition of the family based on the relationships between family members usually resident in the same household.

The general notion of the term 'family' includes relatives whether they live together or not. However in survey research it is necessary to place a practical limit on the extent of family for the purely pragmatic purpose of being able to collect family data. The nominal definition of 'Family composition' is therefore restricted to related people living together in the same dwelling/household.

The concept of 'family' is defined as:

  • Two or more related people who usually live together.

The three fundamental concepts of Family at a broad level are:

  • A family must consist of more than one person.
  • Family members must be related.
  • Family members must live in the same household.

This standard identifies families and different types of families using characteristics such as the size of the family and the relationships between family members.

'Family composition' is an attribute of the counting unit 'family' and, by extension, of the counting unit 'person' for all persons who are members of families.

Operational definition(s)

Operationally, 'family' is defined 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. The basis of a family is formed by identifying the presence of a couple relationship, lone parent-child relationship or other blood relationship. Some households will, therefore, contain more than one family.

Detailed rules are required to define an operational methodology for identifying separate families. These rules are specified in the section on 'Coding procedures' (see 'Classification and Coding' page).

The nominal definition constrains a family within a household and only consists of related people 'usually resident' within that household. The definition of 'household' is therefore fundamental to the definition of 'family'. The important points arising from this definition are:

  • A family must consist of at least two persons, one of whom is at least 15 years of age.
  • A family is identified only from persons who are usually resident within a specific household: family members living in another household are therefore excluded from being part of the same family.
  • Registered and de facto marriages are accorded equal status.
  • Non-related individuals living in the same household (e.g. friend, boarder, housekeeper) are not counted as family members if they are 15 years of age or over.
  • Non-related children under 15 years of age living in the household will be assigned a nominal 'parent' to become part of the family.
  • More than one family can be identified within a single household if more than one group of people satisfy the criteria for forming a family.
  • All related individuals not forming a family within a household, however, are assigned as members of one and only one family. This is an important qualification of the nominal definition.

Operationally, 'Family composition' is defined as:

  • The differentiation of families based on the presence or absence of couple relationships, parent-child relationships, child dependency relationships or other familial relationships, in that order of precedence.

The method for operationalising 'Family composition' is outlined in the section on 'Rules for identifying families' (see 'Classification and Coding' page).

The 'Family composition' of each family is coded from the specific relationships that exist between a single 'family reference person' and each member of that family. 'Family composition' is then coded on the basis of whether the types of relationships listed below are present or not in the family, in the following order of precedence:

  • couple relationship - defined as a registered or de facto marriage
  • parent-child relationship - defined as a relationship between two persons usually resident in the same household. The child is attached to the parent via a natural, adoptive, step, foster or child dependency relationship. (For information on 'nominal children' see the section on 'Discussion of conceptual issues' below)
  • child dependency relationship - defined as including all children under the age of 15 (whether related or unrelated to the family reference person) and those natural, step, adopted or foster children who are full-time students 15-24 years of age
  • 'other' relationship - defined as including all those persons related by blood or by marriage who are not covered by the above relationships.

Consider the example of two elderly brothers living with the family of the daughter of one of the brothers. The daughter's family forms the basic family of the household and the two brothers are both allocated to this family unit as related individuals. The two brothers do not form a separate family in their own right in addition to the daughter's family because they are related to a couple family or one-parent family already present in the household. However, if the two brothers were living in a dwelling with a family to whom they were not related, they would then form a family in their own right and be classified as an 'other family'.

Scope of the variable

The 'Family composition' variable applies to all families.

Discussion of conceptual issues

Nominal child and nominal parent

In many households in Australia the relationships between people and the composition of the households are more diverse than traditional 'nuclear' families. Often the relationships between adults in the household and dependent children (aged under 15 or full-time students aged under 25) would not be captured by the basic coding methods described in the 'Relationship in household' standard. In order to better reflect the nature of those relationships, where to all intents and purposes a 'parent-child' relationship does exist, the ABS uses the concepts of the 'nominal child' and 'nominal parent' to allow these relationships to be captured while maintaining a relatively simple set of family arrangements for analytical purposes. See 'Definition of dependent children and 'nominal child' rules' in the 'Coding procedures' section of the 'Classification and Coding' page for further details.

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