SAMPLING

SCOPE AND COVERAGE

Scope

The Survey of Income and Housing (SIH) collects information by personal interview from usual residents of private dwellings in urban and rural areas of Australia (excluding Very Remote areas), covering about 97% of the people living in Australia. Private dwellings are houses, flats, home units, caravans, garages, tents and other structures that were used as places of residence at the time of interview. Long-stay caravan parks are also included. These are distinct from non-private dwellings which include hotels, boarding schools, boarding houses and institutions. Residents of non-private dwellings are excluded.

Usual residents excludes:

• households that contain members of non-Australian defence forces stationed in Australia
• households that contain diplomatic personnel of overseas governments
• households in areas defined as Very Remote - this has only a minor impact on aggregate estimates, except in the Northern Territory where such households account for about 23% of the population.

For most states and territories, the exclusion of people in Very Remote areas has only a minor impact on any aggregate estimates that are produced because they constitute just a small proportion of the population. Very Remote and Remote areas are defined by the assignment of an Accessibility/Remoteness Index of Australia (ARIA) score. ARIA is a remoteness value (a continuous variable between 0 and 15) that measures the physical distance which separates people in a particular area and where their goods, services and opportunities for social interaction may be accessed.

The ARIA categories, and how ARIA scores are calculated, are further explained in the Australian Statistical Geography Standard (ASGS).

Coverage

Information was collected only from usual residents. Usual residents were residents who regarded the dwelling as their own or main home. Other people present were considered to be visitors and were not asked to participate in the survey.


SAMPLE DESIGN AND SELECTION

Sample design

The SIH sample was designed to produce reliable estimates for broad aggregates of income, wealth, housing data for household residents in private dwellings of Australia, the State and Territories and for the capital cities and rest of state. More detailed estimates should be used with caution, especially for Tasmania, the Northern Territory and the Australian Capital Territory due to smaller samples in these localities. For more information see the 'Reliability of Estimates' section of this publication.

In 2017–18 dwellings were selected through a stratified, multistage cluster design from the private dwelling framework of the ABS Population Survey Master Sample. Selections were distributed across a twelve month enumeration period so that the survey results are representative of income patterns across the year.

SIH selected dwellings, sample loss and selected households

In the 2017–18 SIH, 23,049 dwellings were initially selected for the main sample. When fieldwork commenced some dwellings selected for inclusion in the main sample were found to be out of scope units. Collectively these are referred to as sample loss, and are composed of the following groups:

• dwellings that are out of scope of the survey, under construction, demolished, or converted to non-private dwellings or non-dwellings
• vacant private dwellings
• private dwellings that contain only visitors or out of scope residents (e.g. dwellings occupied by foreign diplomats and their dependants).

In 2017–18, the SIH sample loss was 3,967 dwellings which accounted for 17% of the selected sample.

Sometimes dwellings that have been selected for inclusion in a survey are found to comprise more than one actual dwelling because an additional residence, such as a 'granny flat', has been added to the original dwelling. In such cases, each actual dwelling becomes a separate household. For privacy reasons, residents of a selected dwelling can request that their details be provided separately from other dwelling residents. A separate household is then created for each group of residents. In 2017–18 SIH, 53 selected dwellings were split into two households and 21 were split into three or more households.

A further 5,022 dwellings (22%) did not respond at all to the questionnaire, or did not respond adequately. Most of these were not able to take part in the survey during the collection period or were contacted but either refused to respond or were not able to respond adequately. Other reasons included:

• households affected by death or illness of a household member
• households which did not respond due to communication barriers or because they refused to participate.

This also included 357 households were excluded because the main income earners in the household did not adequately respond to questions about income sources and amounts.

Final SIH sample

Of the selected dwellings (19,082) that were contacted and in scope of the survey, 14,060 (74%) households were included as part of the final estimates.

Survey of Income and Housing, Final sample, 2017–18

	GREATER CAPITAL CITY		REST OF STATE		TOTAL
	Households	Persons(a)	Households	Persons(a)	Households	Persons(a)
	no.	no.	no.	no.	no.	no.
NSW	1 321	2 818	1 030	1 929	2 351	4 747
Vic.	1 333	2 712	1 113	2 064	2 446	4 776
Qld	965	1 856	1 030	1 878	1 995	3 734
SA	1 121	2 150	1 045	1 830	2 166	3 980
WA	1 019	2 031	1 149	2 147	2 168	4 178
Tas.	589	1 058	1 031	1 902	1 620	2 960
NT	428	821	113	203	541	1 024
ACT(b)	773	1 522	. .	. .	773	1 522
Aust.	7 549	14 968	6 511	11 953	14 060	26 921
. . not applicable (a) Number of persons aged 15 years and over (b) Greater Capital City counts for the ACT relate to total ACT