SEIFA - AN OVERVIEW
What is SEIFA?
Uses of SEIFA
SEIFA measures
Further information
WHAT IS SEIFA?
The 2011 Census of Population and Housing provides information on a broad range of social and economic aspects of the Australian population. People using census data are often interested in an overview or summary measure of Census data, rather than looking at individual items. Socio Economic Indexes for Areas (SEIFA) is one such summary measure.
SEIFA is a suite of four indexes that have been created from social and economic Census information. Each index ranks geographic areas across Australia in terms of their relative socio-economic advantage and disadvantage. The four indexes each summarise a slightly different aspect of the socio-economic conditions in an area.
The indexes can be used for a number of different purposes, including targeting areas for business and services, strategic planning and social and economic research. For each index, every geographic area in Australia is given a SEIFA score which measures how relatively ‘advantaged’ or ‘disadvantaged’ that area is compared with other areas in Australia.
The four indexes in SEIFA 2011 are:
Index of Relative Socio-Economic Disadvantage (IRSD)
Index of Relative Socio-Economic Advantage and Disadvantage (IRSAD)
Index of Economic Resources (IER)
Index of Education and Occupation (IEO)
USES OF SEIFA
Some broad guidelines on the appropriate use of SEIFA:
- The indexes are assigned to areas, not to individuals. They indicate the average socio-economic characteristics of the people, families, and households living in the area.
- As measures of socio-economic conditions, the indexes are best interpreted as ordinal measures. They can be used to rank (order) areas, and are also useful to understand the distribution of socio-economic conditions across different areas. Also, the index scores are on an arbitrary scale. The scores do not represent some quantity of advantage or disadvantage. For example, we cannot infer that an area with an index value of 1000 is twice as advantaged as an area with an index value of 500. For ease of interpretation, it is generally recommended that the index rankings and quantiles (e.g. deciles) are used for analysis, rather than using the index scores. Index scores are still provided in the output, and can still be used by more technically adept users.
- The variables that contribute to each index should be considered when deciding which index to use. For example, if a user is interested in finding areas of disadvantage for allocation of services they will probably want to use the Index of Relative Socio-Economic Disadvantage. On the other hand, if a user wanted to focus on finding areas containing relatively high proportions of people in unskilled jobs or with low levels of educational qualifications, the Index of Education and Occupation should be used. A full list of the variables included in each index is provided in each index page.
- The indexes are primarily designed to compare the relative socio-economic characteristics of areas at a given point in time, not to compare individual areas across time (longitudinal analysis using past releases of SEIFA). There are a number of issues that make longitudinal or time series analysis of SEIFA difficult to interpret, and thus it should not be attempted lightly. If comparisons over time are being made, the use of quantiles (e.g. deciles) is recommended, rather than ranks or scores.
SEIFA MEASURES
Each area has a score, rank, decile, and percentile. Rankings within state or territory are also provided. This section explains each of these measures below.
Scores: A score for a Statistical Area Level 1 (SA1) is created by adding together the weighted characteristics of that SA1. The scores for all SA1s are then standardised to a distribution where the average equals 1000 and the standard deviation is 100. For areas larger than SA1, the scores are a population weighted average of the SA1 scores that correspond to the larger area.
A lower score indicates that an area is relatively disadvantaged compared to an area with a higher score. It is important to remember that the scores are an ordinal measure, so care should be take when comparing scores. For example, an area with a score of 1000 is not twice as advantaged as an area with a score of 500.
Ranks: all areas are ordered from the lowest to highest score, then the area with the lowest score is given a rank of 1, the area with the second lowest score is given a rank of 2 and so on, up to the area with the highest score which is given the highest rank.
Deciles: all areas are ordered from lowest to highest 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 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 score.
Percentiles: all areas are ordered from lowest to highest score, then the lowest 1% of areas are given a percentile number of 1, the next lowest 1% are given a percentile number 2 and so on, up to the highest 1% of areas which are given a percentile number of 100. This means that areas are divided up into one hundred equal sized groups, depending on their score.
Ranking within state or territory (rank and decile): all areas within each state or territory are ordered from lowest to highest score, then ranks and deciles are assigned to each area within that state or territory. These state/territory ranks and deciles can only be used to compare areas within a single state or territory.
FURTHER INFORMATION
You can view and download all SEIFA material free of charge from the
Census/SEIFA page of the ABS website.
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