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Household and family characteristics
Information was collected for all selected and non-selected persons in the 2017-18 NHS.
Information was collected about the households and families to which people belong. This information enables some understanding of the situation in which people live, which may impact on their health and related characteristics.
In addition to the items describing the characteristics of household units, basic information is available about each member of the selected households. This enables the circumstances of the respondent to be better understood and provides scope to rework some items (e.g. equivalised income) to suit particular data needs. Items available for each member of the household are:
Relationship in household and family composition are discussed further below. More information on the other topics are available in the Demographic characteristics chapter.
Number of persons in household
This refers to a count of persons who are usual residents of the household dwelling and members of the household to which the respondent belongs.
Additional output items are available including:
This refers to the composition of the household, based on the information about the residents of the household provided by the responsible adult (ARA).
Households are allocated to categories of the 'Household composition' classification on the basis of:
The 'Household composition' classification comprises the following categories:
Further information can be found in Family, Household and Income Unit Variables, 2014 (cat. no. 1286.0).
Family composition of household
This is a new item for NHS 2017-18 which combines the output of the 'Family composition' variable with that of the 'Household composition' variable. It attempts to create family structures within a household based on the relationships of the residents, prioritising any family with dependent children. This structure can include households where there are no familial relationships such as group households or lone person households.
The output categories are:
'Couple family with dependent children only', 'One parent family with dependent children only' and 'Couple only' do not contain any non-dependent children, any related individuals, or any non-family members in the household. 'Other one family households' comprises the 'Family composition' categories 'Other family' and 'One parent family with no children under 15, no dependent students and with non-dependent children'.
For more information about the definition of a Dependent child see the Glossary.
As reported by the selected adult respondent - see Income sources.
Differences in household types and compositions, and their requirements relative to income, can be taken into account by the application of equivalence scales. These scales are a set of ratios which, when applied to the income of different household or income unit types, produce standardised estimates of income which reflect the households' relative well-being. The modified OECD equivalence scale (1994) was used.
Equivalised income is derived by calculating an equivalence factor and then dividing income by that factor. The equivalence factor is built up by allocating points to each person in the household unit and summing those points. One point is allocated to the first adult in the unit, 0.5 points for each other person aged 15 years and over, and 0.3 points for each person aged less than 15 years. For example:
Equivalised income is available in dollar amounts and deciles.
Income deciles and quintiles
Income deciles are groupings that result from ranking either all households or all persons in the population in ascending order according to some characteristic, such as income, and then dividing the population into ten equal groups, each comprising 10% of the estimated population. The first decile contains the bottom 10%, the second decile contains the next 10%, and so on. Quintiles are derived by adding together the first and second decile for the first quintile, third and fourth decile for the second quintile, and so on.
To assist in the use and interpretation of income deciles or quintiles at the person or household level, it is necessary to exclude income which is not stated or not known. If one or more of the contributing person records in a household has a value of 'not known' or 'not stated', then household income and derived income deciles are set to '98. Not stated' or '99. Not known' as it is not possible to determine an accurate value. Records with these codes should be excluded when categorising higher income values, and when calculating means, medians and other summary statistics.
For the 2017-18 NHS, the dollar ranges covered by deciles in all income items can be found at Appendix 5: Income deciles.
Socio-economic Indexes for Areas (SEIFAs)
Socio-Economic Indexes for Areas (SEIFA) is a product developed by the ABS that ranks areas in Australia according to relative socio-economic advantage and disadvantage. The indexes are based on information from the five-yearly Census.
SEIFA 2016 is the latest version of this product and consists of four indexes:
Each index is a summary of a different subset of Census variables and focuses on a different aspect of socio-economic advantage and disadvantage.
Data from the 2017-18 NHS has been output according to the SEIFA 2016 as well as the previous version SEIFA 2011. It is emphasised, however, that these indexes relate to the area in which the survey respondent lived, and are not necessarily indicative of an individual respondent's socio-economic status. The 2011 index scores have been mapped to the SA1 and SA2 levels on both a National and State basis. The Index of Relative Socio-economic Disadvantage is the SEIFA index most frequently used for analysis of health characteristics.
For further information about the 2016 indexes, see Census of Population and Housing: Socio-Economic Indexes for Areas (SEIFA), Australia, 2016 (cat. no. 2033.0.55.001).
SEIFAs are commonly used to group populations into deciles or quintiles of a particular index. In the NHS, this enables comparisons to be made between the health characteristics, for example, of people living in less advantaged areas with those in more advantaged areas.
SEIFA deciles/quintiles can be derived in two ways - area-based and population-based.
All areas are ordered from lowest to highest index score, then the lowest 10% of areas are given a decile number of 1, the next lowest 10% of areas are given a decile number of 2 and so on, up to the highest 10% of areas which are given a decile number of 10. This means that areas are divided up into ten equal sized groups, depending on their index score.
An alternative way of defining the deciles is to divide them into ten equal groups based on the number of people living in those areas. These deciles contain an equal number of people (or at least as can be best achieved) in each group, rather than an equal number of areas. These are called population-based deciles.
For the NHS, SEIFA decile items have been derived for Area-based groupings. Because all SA1, SA2, LGA, POA, SSC, SLA are not equal in size and because the NHS sample is not selected to ensure an equal sample distribution at these lower level geographies, this method does not result in an equal number of people (either records or weighted estimates) in each decile/quintile.
Confusion can arise about the ordering of the deciles/quintiles created from SEIFA indexes. ABS constructs all four indexes so that relatively disadvantaged areas (e.g. areas with many low income recipients) have low index values, and relatively advantaged areas (e.g. areas with many high income recipients) have high index values. Correspondingly, in ABS publications and other outputs, SEIFA deciles are numbered from decile 1 or lowest decile (most disadvantaged), to decile 10 or highest decile (least disadvantaged). Quintiles are labelled similarly.
For consistency, this ordering applies to all indexes, irrespective of whether they are named as indexes of advantage and/or disadvantage. Care needs to be taken in comparing SEIFA analyses undertaken by different agencies, as quintiles or deciles may be labelled in reverse order to the standard ABS order.
The composition of specific families within households is available on the All Persons level. This can provide a more detailed understanding of the family unit to which a person belongs than provided at the Household level.
'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 'family composition' of a particular family is created through the relationships that exist between a single 'responsible adult' and each other member of that family living in the household. Family composition is then allocated on the basis of whether the types of relationships given below are present or not in the family in the following order of precedence:
Family composition is categorised as follows:
The definition of family used for the NHS is a more restrictive definition than the ordinary notion of the term 'family' which generally includes relatives whether they live together or not. This is a reflection of the fact that for survey-based research it is necessary to place some physical bound on the extent of family, for the purposes of being able to collect family data.
Relationship in household
Relationship in household was derived from information supplied by the responsible adult (ARA) who answered the initial survey questions for each household, about all usual residents of the household. It describes the relationship of each person in a household to the ARA (i.e. wife, son, not related). Output categories are:
For more information about the definition of a child under 15 and dependent student see Dependent child see the Glossary.
The questionnaire, data items and related output categories for this topic are available in pdf / Excel spreadsheet format from the Downloads page of this product.
Comparability with 2014-15
All items above are considered directly comparable between the 2017-18 and 2014-15 NHS except for Family composition of household which was added in NHS 2017-18.
More information regarding comparisons between 2014-15 NHS and previous cycles is available in the National Health Survey: Users' Guide, 2014-15 (cat. no. 4363.0).
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