Appendix B: Technical notes

This appendix covers definitions and classifications used, and the presentation of data in this report.

Definitions and classifications

If not otherwise indicated, data elements were defined according to the definitions available online for the following collections.

Hospital peer groups

In some tables, hospitals have been presented using the AIHW’s hospital peer group classification:

  • Principal referral hospitals provide a very broad range of services and have very large patient volumes. Most include an intensive care unit, a cardiac surgery unit, a neurosurgery unit, an infectious diseases unit and a 24-hour emergency department
  • Women’s and children’s hospitals provide specialised treatment for women and/or children
  • Public acute group A hospitals provide a wide range of services (but narrower than the Principal referral group) to a large number of patients and are usually situated in metropolitan centres or inner regional areas. Most have an intensive care unit and a 24 hour emergency department and a range of specialist units.
  • Public acute group B hospitals provide a narrower range of services than the Principal referral and Public acute group A hospitals. They have a range of specialist units, potentially including obstetrics, paediatrics, psychiatric and oncology units
  • Other public hospitals include a range of different types of hospitals that are generally smaller than the Public acute group B hospitals. This group may include small and very small hospitals providing acute care, hospitals specialising in subacute and non-acute care, psychiatric hospitals and outpatient hospitals.

For more information about public hospital peer groups, see the AIHW publication Australian hospital peer groups.

Geographical classifications

Data on geographical location are collected on the area of usual residence of patients in the NNAP(el)D. These data are specified in the NBEDS as state or territory of residence and by Statistical Area Level 2 (SA2), which is a small area unit within the Australian Bureau of Statistics (ABS) Australian Statistical Geography Standard (ASGS).

Remoteness areas

The patient’s area of usual residence can be used to derive its remoteness category.

Remoteness categories divide Australia into areas depending on distances from population centres, using the Australian Bureau of Statistics (ABS) Australian Statistical Geography Standard (ASGS) Remoteness Structure 2016 (ABS 2016).

The ABS’s ASGS Remoteness Structure 2016 categorises geographical areas in Australia into remoteness areas.

The classification is as follows:

  • Major cities—for example, Sydney, Melbourne, Brisbane, Adelaide, Perth, Canberra and Newcastle
  • Inner regional—for example, Hobart, Launceston, Wagga Wagga, Bendigo and Murray Bridge
  • Outer regional—for example, Darwin, Moree, Mildura, Cairns, Charters Towers, Whyalla and Albany
  • Remote—for example, Port Lincoln, Esperance, Queenstown and Alice Springs
  • Very remote—for example, Mount Isa, Cobar, Coober Pedy, Port Hedland and Tennant Creek.

Reporting data on area of usual residence of the patient

Area of usual residence was provided as SA1 or SA2 for the NNAP(el)D.

The AIHW mapped the provided SA2 codes to remoteness area categories based on the ABS’s ASGS Remoteness Structure 2016. These mappings were undertaken on a probabilistic basis as necessary, using ABS correspondence information describing the distribution of the population by remoteness areas and SA2s. Because of the probabilistic nature of this mapping, the SA2 and remoteness area data for individual records may not be accurate; however, the overall distribution of records by geographical areas is considered useful.

Socioeconomic status

Data on socioeconomic status groups are defined using the ABS’s Socio-Economic Indexes for Areas 2016 (SEIFA 2016).

The SEIFA 2016 data are generated by the ABS using a combination of 2016 Census data, including income; education; health problems/disability; access to internet; occupation/unemployment; wealth and living conditions; dwellings without motor vehicles; rent paid; mortgage repayments; and dwelling size. Composite scores are averaged across all people living in areas and defined for areas based on the Census collection districts.

The SEIFA Index of Relative Disadvantage (IRD) is one of the ABS’s SEIFA indexes. The relative disadvantage scores indicate the collective socioeconomic status of the people living in an area, with reference to the situation and standards applying in the wider community at a given point in time. A relatively disadvantaged area is likely to have a high proportion of relatively disadvantaged people. However, such an area is also likely to contain people who are not disadvantaged, as well as people who are relatively advantaged.

Counts of non-admitted patient service events by socioeconomic status were generated by the AIHW using the IRD scores for the SA2 of usual residence of the patient reported for each service event. The ‘1—Lowest’ group represents the areas containing the 20% of the national population with the most disadvantage, and the ‘5—Highest’ group represents the areas containing the 20% of the national population with the least disadvantage. These SES groups do not necessarily represent 20% of the population in each jurisdiction.

Presentation of data

Tables in this report that present numbers of non-admitted patient service events, include both individual and group service events.

Data are presented by the state or territory of the hospital, not by the state or territory of usual residence of the patient. The exceptions to this occur in the presentation of data by remoteness area and socioeconomic status of area of usual residence—which present data at a national level based on the place of usual residence of the patient. The totals in tables include data only for those states and territories for which data were available, as indicated in the tables.

Throughout the publication, percentages may not add up to 100.0 because of rounding. Percentages printed as 0.0 or 0 generally indicate a zero. The symbol ‘<0.1’ denotes less than 0.05 but greater than 0.

Suppression of data

The AIHW operates under a strict privacy regime which has its basis in Section 29 of the Australian Institute of Health and Welfare Act 1987 (AIHW Act). Section 29 requires that confidentiality of data relating to persons (living and deceased) and organisations be maintained. The Privacy Act 1988 governs confidentiality of information about living individuals.

The AIHW is committed to reporting that maximises the value of information released for users while being statistically reliable and meeting legislative requirements described above.

The abbreviation ‘n.p.’ is used in tables to denote the suppression of data. Data (cells) in tables may be suppressed to maintain the privacy or confidentiality of a person or organisation, or because a proportion or other measure is related to a small number of events and may therefore not be reliable.

Data may also be suppressed to avoid attribute disclosure. Where necessary, other cells in the table may also be suppressed to prevent calculation of the confidential information. Unless otherwise noted, the totals in these tables include the suppressed information.


ABS (Australian Bureau of Statistics) 2016. Australian Statistical Geography Standard (ASGS): Volume 1—Main Structure and Greater Capital City Statistical Areas. ABS cat. no. 1270.0.55.001. Canberra: ABS. Available on the ABS website.

ABS 2018. Census of population and housing: Socio-economic Indexes for Areas (SEIFA), Australia, 2016. ABS cat. no. 2033.0. Canberra: ABS. Available on the ABS website

AIHW 2015. Australian hospital peer groups. Health services series no. 66. Cat. no. HSE 170. Canberra: AIHW. Available on the AIHW website.