Socio-Economic Indexes for Areas (SEIFA): Technical Paper

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 2021 is based on Census 2021 data, and consists of four indexes, each focusing on a different aspect of socio-economic advantage and disadvantage, summarising a different subset of Census variables.

Some common uses of SEIFA include:  

• determining areas that require funding and services,
• identifying new business opportunities, and
• assisting research into the relationship between socio-economic disadvantage and various social outcomes.

This paper provides information on the concepts, data, and methods used to create SEIFA 2021. The paper also contains discussion of the correct interpretation and appropriate use of the indexes.

This paper is intended to be a comprehensive reference for SEIFA 2021. Refer to Methodology for basic information that has been prepared for a general audience.

A relative measure of socio-economic disadvantage was first produced by the ABS following the 1971 Census. Socio Economic Indexes for Areas (SEIFA), in its present form, was first produced from the 1986 Census data.

This section highlights some important features of SEIFA 2021, and how they compare with SEIFA 2016.

SEIFA 2021 consists of the same four indexes as produced for SEIFA 2001, 2006, 2011 and 2016, each referring to the general population:

• the Index of Relative Socio-economic Disadvantage (IRSD),
• the Index of Relative Socio-economic Advantage and Disadvantage (IRSAD),
• the Index of Economic Resources (IER), and
• the Index of Education and Occupation (IEO).

We have generally aimed to maintain consistency between SEIFA 2021 and the previous release. However, some changes have been made and are described below.

SEIFA 2021 uses the Australian Statistical Geography Standard (ASGS) Edition 3 (2021).  The structure of the ASGS Edition 3 is similar to the structure of ASGS Edition 2 (2016), though there have been updates to SA1 boundaries in some areas. In this version of the ASGS, State Suburbs (SSCs) are now referred to as Suburbs and Localities (SALs). SALs and Postal Areas (POAs) are constructed from Mesh Blocks rather than SA1s. For more information about the ASGS, refer to Changes from the previous edition of the ASGS.

Some variables were updated in line with new classification standards. For example, for the 2016 SEIFA, Australian and New Zealand Classification of Occupations, 2013 (ANZSCO), version 1.2A was used. For 2021, the updated version, ANZSCO version 1.3, was used, resulting in some changes to skill level and some title changes. Variables using cut-off values in their definitions, such as high and low income, were updated to use new cut-off values. For more information about how the cut-off values were selected, refer to the description of candidate SEIFA variables. Census 2021 did not collect information about dwelling internet connection, and so the NONET variable from SEIFA 2016 could not be considered for inclusion in SEIFA 2021.

SEIFA output includes a general introduction to SEIFA 2021, a basic Methodology, this Technical Paper and data which can be sourced from:

• Data cubes for a range of geographies
• TableBuilder data
• DataExplorer data (available after 11:30 on 27 April 2023) 
• Interactive maps (available on 9 May 2023).

To set some context for the rest of this paper, it is worth briefly touching on some important characteristics of the indexes.

The indexes are assigned to areas, not to individuals. They indicate the collective socio-economic characteristics of the people living in an area.

As measures of socio-economic conditions, the indexes are best interpreted as ordinal measures that rank areas. The index scores are based on an arbitrary numerical scale and do not represent a quantity of advantage or disadvantage.

For ease of interpretation, we generally recommend using the index rankings and quantiles (e.g. deciles) for analysis, rather than using the index scores. However, index scores are still provided in the output and can be used for more sophisticated analyses.

Each index is constructed based on a weighted combination of selected variables. The indexes are dependent on the set of variables chosen for the analysis. A different set of underlying variables would result in a different index.

The indexes are primarily designed to compare the relative socio-economic characteristics of areas at a given point in time. It can be very difficult to perform useful longitudinal or time series analysis, and this sort of analysis should be undertaken with care.

There is more discussion of these points in Using and Interpreting SEIFA.