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2039.0 - Information Paper: An Introduction to Socio-Economic Indexes for Areas (SEIFA), 2006  
Latest ISSUE Released at 11:30 AM (CANBERRA TIME) 26/03/2008   
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CHAPTER 2 WHAT IS SEIFA? FREQUENTLY ASKED QUESTIONS



INTRODUCTION AND MAIN POINTS

This chapter describes the SEIFA numbers and briefly considers the most frequently asked questions about SEIFA. Some of these issues are discussed in greater detail in later chapters.

  • WHAT ARE THE SOCIO-ECONOMIC INDEXES FOR AREAS (SEIFA)?
  • WHAT ARE THE FOUR SETS OF NUMBERS IN EACH INDEX?
  • THE GEOGRAPHIC AREAS
  • WHICH INDEX DO I USE?
  • OTHER FREQUENTLY ASKED QUESTIONS

Main points of Chapter 2


Some common issues when using SEIFA, as well as some of the limitations of SEIFA, are listed below. These issues are discussed in this chapter, and in more detail in later chapters.

  • It is difficult to capture an abstract concept like socio-economic disadvantage. Please refer to Chapters 1 and 3 for more information.
  • The indexes do not capture every aspect of socio-economic disadvantage. Please refer to Chapter 5 for more information.
  • Comparison with previous indexes is not recommended. Please refer to Chapter 5 for more information.
  • The method used to create the indexes is called Principal Components Analysis. Every method has strengths and limitations. Please refer to Chapters 3 and 5 for more information.
  • SEIFA is a summary of people in an area and does not apply to an individual person or dwelling. Every area has a diverse range of different people and dwellings. The SEIFA indexes represent the general level of socio-economic disadvantage of all the people in the area in which a person lives, not the person themselves. Please refer to Chapter 5 for more information.


WHAT ARE THE SOCIO-ECONOMIC INDEXES FOR AREAS (SEIFA)?

SEIFA is a suite of four summary measures that have been created from Census information. Each index summarises a different aspect of the socio-economic conditions in an area, and therefore summarises a different set of social and economic information. The indexes can be used to explore different aspects of socio-economic conditions by geographic areas. For each index, every geographic area in Australia is given a SEIFA number which shows how relatively 'disadvantaged' that area is compared with other areas in Australia.


The four indexes in SEIFA 2006 are:

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

Where can I find the SEIFA indexes?


The SEIFA indexes are available free of charge from the ABS website, cat. no. 2033.0.55.001 Census of Population and Housing: Socio-Economic Indexes for Areas (SEIFA), Australia - Data only, 2006.(footnote 1)


In what format are the indexes available?


The SEIFA indexes are available in Excel spreadsheet format.

  • A separate downloadable spreadsheet is available for each of the five geographical areas: Collection District (CD), Statistical Local Area (SLA), Local Government Area (LGA), Postal Area (POA) and State Suburbs (SSC).(footnote 2)
      • Each spreadsheet contains the four SEIFA indexes that have been created for that geographical area, each on a separate worksheet. For example, the CD level spreadsheet contains the four CD level IRSD, IRSAD, IER and IEO indexes on separate worksheets. There is also a Summary worksheet containing the scores of all the indexes. The CD level spreadsheet also includes a worksheet with geographic concordances.
      • The worksheet for each index shows:
          • the geographic area code. For example, the CD level spreadsheet lists the CD codes;
          • the number of people who usually resided in the area on Census Night;
          • the set of four index numbers, being the SEIFA score, rank, decile and percentile numbers (as described below) for the area; and
          • a State rank, a State decile and a State percentile number, which are applicable only within each State/Territory. Please refer to the Glossary for further details on these State numbers.
      • For example, the CD level index for the Index of Economic Resources has a list of 37,457 CDs, with the IER score, IER rank, IER decile and IER percentile number for each CD.
  • Previously, SEIFA has released separate indexes for Statistical Subdivisions (SSD), Statistical Divisions (SD) and States. These indexes have not been created for 2006 SEIFA, however a spreadsheet tool is available that shows population distributions of CD scores within these areas. This tool is discussed further in Chapter 5.


WHAT ARE THE FOUR SETS OF NUMBERS IN EACH INDEX?

SEIFA numbers


SEIFA is a tool that compares an area with other areas. It can be likened to a football premiership table. Just as a team that finished the season with 40 points cannot claim to be twice as good as a team that finishes the season with 20 points, so an area that has a SEIFA score of 1200 cannot claim to be twice as advantaged as an area that scored 600.


Each of the four indexes are released in four forms: as a 'score', as a 'rank', as a 'decile' and as a 'percentile'. Therefore, for each index, every geographical area is given a score number, a rank number, a decile number and as a percentile number. These numbers all rank areas in order of disadvantage, but are used for different purposes.


What is a SEIFA score?


A SEIFA score is created using information about people and households in a particular area. This score is standardised against a mean of 1000 with a standard deviation of 100. This means that the average SEIFA score will be 1000 and the middle two-thirds of SEIFA scores will fall between 900 and 1100 (approximately). (Refer to the Glossary for more on standardisation). A SEIFA score provides more information and is used for more sophisticated analysis. Deciles should be used for most analyses.


What is a SEIFA rank?


To determine the SEIFA rank, all the areas are ordered from lowest score to highest score. 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, being 37,457 for a collection district (CD) index.


What is a SEIFA decile?


Deciles divide a distribution into ten equal groups. In the case of SEIFA, the distribution of scores is divided into ten equal groups. The lowest scoring 10% of areas are given a decile number of 1, the second-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.


What is a SEIFA percentile?


Percentiles divide a distribution into 100 equal groups. In the case of SEIFA, the distribution of scores is divided into 100 equal groups. The lowest scoring 1% of areas are given a percentile number of 1, the second-lowest 1% of areas are given a percentile number of 2 and so on, up to the highest 1% of areas which are given a percentile number of 100. SEIFA percentiles are provided to allow users to create their own groupings, such as quartiles (which contain 25% of CDs).


Refer to the Glossary for information on State ranks, State deciles and State percentiles.



THE GEOGRAPHIC AREAS

What type of areas are available in SEIFA?


The 2006 indexes are available for the following geographic areas:

  • Collection District (CD);
  • Statistical Local Area (SLA);
  • Local Government Area (LGA);
  • Postal Area (POA); and
  • State Suburb (SSC).

Each type of area has its own set of scores, ranks, deciles and percentiles.


The smallest area for which SEIFA is available is a Census Collection District (CD). A CD is equivalent to a group of suburban blocks, roughly 250 households in a urban area. However, in a rural area, a CD can represent far fewer households. Both SLAs and LGAs are standard geographic areas which are based on CDs. POA is not an ASGC standard geographic area, but have been created by the ABS to match Australia Post postcodes as closely as possible. SSC is not an ASGC standard geographic area, but have been created by the ABS to match suburbs as closely as possible.(footnote 3) Chapter 4 and the Glossary discuss these geographic areas further.


Can I use other areas?


If you wish to analyse a different type of area other than those available for SEIFA, then you may wish to create your own index. This is discussed later in this chapter.


Why is a SEIFA score not created for every CD?


It is not always meaningful to give a CD a score. For example, the CD may be an airport or a large office block, with no-one actually residing in the area. In addition, there may be very few people in the area, or only a few who responded to the Census questions. If there are only a few people or responses, then it becomes difficult to calculate a reliable score.(footnote 4) Additionally, those who did respond may not be representative of the area as a whole. Confidentiality issues can also arise when there are only a few people in an area.


Areas were not given a score if they fell into one of the following categories:

  • No usual residents (which accounted for 49% of excluded CDs);
  • Number of people was ten or fewer (which accounted for another 13% of excluded CDs);
  • Number of employed was five or fewer;
  • Proportion of people not responding to the following Census questions (as appropriate) was 70% or more: occupation, labour force status, type educational institution, or non-school qualifications;
  • Proportion of people in households for which equivalised household income could not be calculated was 70% or more.
  • Number of occupied private dwellings was five or fewer;
  • Proportion of people residing in non-private dwellings was 80% or more; or
  • The area was classified as off-shore, shipping or migratory.

Please refer to the Technical Paper for further information.


Are area boundaries comparable to previous years?


SEIFA uses ABS geographic standards to determine area boundaries. However, these standards change over time for various reasons. For example, when new housing subdivisions are built or government area boundaries are revised, standards must be revised to match. There can be many changes in the five years since SEIFA indexes were last released. For example, in 1996 there were 34,422 CDs in Australia, with 37,207 CDs in 2001, and 38,704 CDs in 2006. Around 14% of 2006 CDs cannot be directly compared to 2001 CDs. Chapter 7 lists references for more information on ABS geographic standards.


How can a street have two different SEIFA scores?


Because collection districts are based on suburban blocks, the blocks on either side of the same street could fall into different collection districts. If a street is long enough, it could also span two collection districts.


Why does my suburb have multiple SEIFA scores?


Each CD is given its own SEIFA score. However, because CDs do not have names (only a code), it is not immediately obvious where a particular CD is located in Australia. As discussed above, CDs can be matched to other geographic areas that do have names. For example, a CD may be matched back to the SLA of Parramatta (C) - Inner. There are two important points to note. First, as discussed above, separate SEIFA indexes are created for different geographies (CD, SLA, LGA, POA, SSC). It is important to be clear about which index you are using. If you are using the SLA index, then there will be only one score for the SLA of Parramatta (C) - Inner. However, if you are using the CD index, then there are many CDs within an SLA, and each CD will have its own SEIFA score. For example, there are 53 CDs within the SLA of Parramatta (C) - Inner. Second, the SLA name itself can cause confusion if it shares the same name as a suburb, such as the example used here. Please refer to Chapter 4 for a map of CD scores in an example SLA, and a discussion of the geographies used in SEIFA.



WHICH INDEX DO I USE?

Index selection


Four SEIFA indexes are available, and the choice of index depends on the analysis to be undertaken. There are two general indexes of socio-economic disadvantage, an index for economic resources and an index for education and occupation. It is important to be clear about the concept you are trying to capture before selecting an index. In addition to the discussion below, please also refer to Chapter 4, and to the Appendix for a full list of variables included in each index.


Why does the same area have a different rank for each index?


Each index aims to capture a slightly different aspect of relative disadvantage and is constructed using different variables. It is therefore possible for the same area to have different rankings on each index. For example, it is possible for an area to rank relatively highly in the Disadvantage index, but not in the Advantage and Disadvantage index, because these indexes include different variables.


Index of Relative Socio-economic Disadvantage (IRSD)


This index is a general socio-economic index that summarises a wide range of information about the economic and social resources of people and households within an area. Because this index focuses on disadvantage, only measures of relative disadvantage are included. This means that, unlike the other indexes, a high score (or decile) reflects a relative lack of disadvantage rather than relative advantage, as shown in figure 2.1.

Figure 2.1 IRSD, Interpretation of Deciles
Figure 2.1 IRSD, Interpretation of Deciles



This index summarises 17 different measures, such as low income, low education, high unemployment and unskilled occupations.


A low score indicates relatively greater disadvantage in general. For example, an area could have a low score if there are (among other things):

  • many households with low income, many people with no qualifications, or many people in low skilled occupations.

A high score indicates a relative lack of disadvantage in general. For example, an area may have a high score if there are (among other things):
  • few households with low incomes, few people with no qualifications or in low skilled occupations.

This index is preferred in situations where the user:
  • wants to look at disadvantage and lack of disadvantage; and
  • wants a broad measure of disadvantage, rather than a specific measure (such as low income).

An example would be where a user:
  • wants to ensure an allocation of funds goes to disadvantaged areas.

We do not recommend using this index if the user:
  • is analysing information that was used to create this index, such as Indigenous status;(footnote 5) or
  • wants to look at both advantage and disadvantage.

Index of Relative Socio-economic Advantage and Disadvantage (IRSAD)


This index is also a general socio-economic index that was created using measures of relative disadvantage (similar to those used in the Index of Relative Disadvantage), as well as measures of relative advantage. As shown in figure 2.2, a high score (or decile) reflects relative advantage.

Figure 2.2 IRSAD, Interpretation of Deciles
Figure 2.2 IRSAD, Interpretation of Deciles



There are 21 measures included, such as: low or high income, internet connection, occupation and education. This index does not include Indigenous status.


A low score indicates relatively greater disadvantage and a lack of advantage in general. For example, an area could have a low score if there are (among other things):

  • many households with low incomes, or many people in unskilled occupations; AND
  • few households with high incomes, or few people in skilled occupations.

A high score indicates a relative lack of disadvantage and greater advantage in general. For example, an area may have a high score if there are (among other things):
  • many households with high incomes, or many people in skilled occupations; AND
  • few households with low incomes, or few people in unskilled occupations.

This index is preferred in situations where the user:
  • is not looking only at disadvantage and lack of disadvantage;
  • wants advantage to offset any disadvantage in an area;
  • is using a variable in their analysis, such as Indigenous status, that has been included in the construction of another index but not this index; or
  • is unable to identify a specific aspect of disadvantage, such as income, that is important to their particular analysis.(footnote 6)

An example would be where a user:
  • considers the issue being examined to be affected by both advantage and disadvantage. For example, this index would be suitable if the user is looking at health status and anticipates disadvantaged people to have worse health and advantaged people to have better health. If disadvantaged people are expected to have worse health, but it is less-disadvantaged people (rather than advantaged people) that are expected to have better health, then the Index of Relative Disadvantage would be more appropriate to use; or
  • is analysing information that is not included in the index, such as home ownership or Indigenous status.

We do not recommend using this index if the user:
  • is analysing information that has already been included in the index, such as access to broadband internet connection; or
  • is only interested in disadvantage.

Index of Economic Resources (IER)


This index reflects the economic resources of households within an area. There are 15 variables included to measure a wide range of concepts, such as: household income, housing expenditures (e.g. rent) and wealth (e.g. home ownership). Some of these are new to the 2006 IER, which introduced additional measures to better capture economic resources, such as unemployment and ownership of an unincorporated enterprise. However, some important information, such as superannuation, was not included as it was not collected in the Census. This index does not include education or occupation measures. Similar to the Index of Relative Advantage and Disadvantage, this index includes measures that capture both 'low' and 'high' access to economic resources.


A low score indicates a relative lack of access to economic resources in general. For example, an area may have a low score if there are:

  • many households with low income, or many households paying low rent; AND
  • few households with high income, or few owned homes.

A high score indicates relatively greater access to economic resources in general. For example, an area may have a high score if there are:
  • many households with high income, or many owned homes; AND
  • few low income households, or few households paying low rent.

This index is preferred in situations where the user:
  • is looking specifically at access to economic resources and the associated ability to participate in society.

We do not recommend using this index if the user:
  • is only interested in disadvantage, as this index measures both advantage and disadvantage; or
  • is interested in a more specific measure, such as income; or
  • is interested in a more general measure, such as the Index of Relative Advantage and Disadvantage; or
  • is also analysing information that was included in the index, such as household income.

Index of Education and Occupation (IEO)


This index reflects the general level of education and occupation-related skills of people within an area. There are nine measures included in this index. The education information in this index includes qualifications achieved and whether further education is being undertaken. The occupation information in this index includes occupations that require a high level of skills, occupations that require a low level of skills, as well as unemployment. This index does not include any income measures. This index includes both 'low' and 'high' measures of education and occupation.


This index is highly correlated with the Index of Relative Disadvantage and the Index of Relative Advantage and Disadvantage, but has only a medium correlation with the Index of Economic Resources (which is not unexpected as these two indexes have only one variable in common).


A low score indicates relatively lower education and occupation status of people in the area in general. For example, an area could have a low score if there are:

  • many people with few qualifications, or unemployed or in low skilled occupations; AND
  • few people with a high level of qualifications or in highly skilled occupations.

A high score indicates relatively higher education and occupation status of people in the area in general. For example, an area could have a high score if there are:
  • many people with higher education qualifications or in highly skilled occupations; AND
  • few people without qualifications or in low skilled occupations.

This index is preferred in situations where the user:
  • is interested in occupation and education variables; or
  • is interested in an index that does not include income; or
  • is interested in investigating the economic resources and the education and occupation separately.(footnote 7)

We do not recommend using this index if the user:
  • is only interested in disadvantage (not advantage); or
  • is interested in a more general measure of disadvantage and advantage; or
  • is analysing information that has already been included in the index, such as unemployment.

The index scores are described further in Chapter 4.



OTHER FREQUENTLY ASKED QUESTIONS

How do I match SEIFA to my data?


First, ensure that the SEIFA geographic areas match the geography areas of your data set. For example, if your analysis uses Census Collection Districts (CDs) then use the SEIFA index for CDs. Use the smallest area that your data set allows, preferably CDs.


Second, it should be noted that 2006 SEIFA geographic boundaries are based on the 2006 Australian Standard Geographic Classification (ASGC); 2001 SEIFA boundaries are based on the 2001 ASGC, and so on. Therefore, the 2006 SEIFA is based on information about people and households within the 2006 ASGC boundaries. Boundary changes mean that information based on the boundaries of one ASGC release will not necessarily be consistent with another ASGC release. Check which ASGC your survey data used. Always check the geographic standard used in the collection of your data, as differences can substantially affect comparisons.


Third, match (as closely as possible) the time of your data collection with the year the SEIFA data was collected. For example, if your survey was undertaken in 2006, then use the 2006 SEIFA as this was based on data collected in the 2006 Census.


In practice, you will rarely be able to perfectly match the timing of the data collection and the ASGC boundaries between SEIFA and your survey.


For how many years are SEIFA indexes available?


A type of socio-economic disadvantage measure was first produced using information from the 1971 Census. In their present form, the indexes were first produced in 1990 (using 1986 Census data). Later indexes have been produced in 1994 (1991 Census), 1998 (1996 Census), 2003 (2001 Census) and 2008 (2006 Census). The indexes from 1986 onwards are available on the ABS website.


Can I compare SEIFA across time?


This is a common question and many users would like to be able to compare an area's SEIFA score over time, however this is not recommended. There are a number of reasons for caution:

  • SEIFA is based on information measured at a certain point in time. The indexes are based on the complex interactions between this information. Because the world changes, this information also changes, which results in changes to the indexes.
  • A change in the rank of a particular area is not necessarily a reflection of changes within that area. For example, if an area has a rank of 19,000 in 2001 and a rank of 20,000 in 2006, this cannot be interpreted as the area being less disadvantaged than before. This higher rank may be due to other areas becoming more disadvantaged, rather than to any change within that particular area.
  • While consistency in the construction of SEIFA is important, some changes are made where important or necessary.
  • As discussed earlier in Chapter 2, the total number of areas measured also changes with each release, affecting the ranks. The 2001 SEIFA CD ranks ranged between 1 - 35,695; the 2006 SEIFA CD ranks ranged between 1 - 37,457. SEIFA is based on geography standards which evolve over time to include new CDs: the 2001 ASGC has 37,209 CDs and the 2006 ASGC has 38,704 CDs. In addition, some of these CDs are excluded from SEIFA and the number of excluded CDs also changes.
  • As discussed earlier in Chapter 2, the ASGC area boundaries can change. If an area boundary changes to include a different group of households, then the overall characteristics of the area may change even if all the other households in the area do not.

For these reasons, comparing SEIFA over time can lead to misleading results. If you must compare the SEIFA score of an area over time, it is best to state that an area had:
  • a SEIFA decile of 4 in 2001, and 5 in 2006; or
  • a SEIFA rank of 19,000 in 2001, and 20,000 in 2006; or
  • a SEIFA score of 977 in 2001, and 990 in 2006.

We strongly recommend that users do not go further and state that an area improved by 13 'SEIFAs', or even that the area has 'improved' at all.


We recommend the use of deciles, rather than ranks or scores. The ranks are impacted by the different number of CDs included in each release. For example, if a CD has a rank of 50 in 2001 and a rank of 100 in 2006, this could be simply due to the larger number of CDs included in the 2006 index, rather than any change in the area. In addition, using the scores may imply a level of accuracy that is not provided by a general measure of relative disadvantage like SEIFA. Ranks and scores are appropriate only for more technical use. Further, we recommend that the extreme deciles be compared, because these tend to be more stable over time.


This issue is briefly discussed again in Chapter 5.


Is everyone disadvantaged in a low score area?


No. It is not correct to use SEIFA to represent a person or a household.


A SEIFA score is an average of people and households within a given area, therefore not everyone in the area would have that same score. Using the football analogy, a team with some excellent players may not necessarily qualify for the finals. In the same way, an area that SEIFA rates as relatively disadvantaged could have some advantaged households; just as an area ranked as relatively advantaged could have some households that are relatively disadvantaged.


SEIFA provides summary information about the people in an area, not information about an individual person in an area. If you have person-level data and you want to use SEIFA, then you need to be careful in your interpretation. Area-level measures do provide some information about individual people, however this is only part of the story. Area-effects and personal information can both be relevant to you analysis.(footnote 8) SEIFA represents the general socio-economic status of the area in which an individual lives. SEIFA says nothing about the socio-economic status of a particular person or household.


For example, a person could be employed in a high-paying job but live in an area of generally high unemployment and low income. In this situation, the person may be quite well-off even though the area's SEIFA score indicates relative disadvantage. If used in a person-level analysis, this could be interpreted as: "the area in which the person lives is relatively disadvantaged". It is not correct to use SEIFA to say a particular person is relatively disadvantaged, because other data would be needed to draw this conclusion.


What information was / was not used to construct SEIFA?


Measures deemed to represent different aspects of relative socio-economic disadvantage were considered for inclusion in the indexes. The data items were sourced only from the Census as this is the best source of detailed information within small geographic areas. However, this approach limits the range of data available because some information is difficult or sensitive to request. Therefore, some information was not included in SEIFA, including:

  • Access to infrastructure, which impacts on people's ability to participate in society. Examples include access to schools, community services, shops, transport and medical facilities.
  • Wealth information (such as the value of assets) directly impacts on the economic resources of households and the ability of people to participate in society. However, this concept is difficult to measure. Although the 2006 Index of Economic Resources has included more information that reflect aspects of wealth than earlier indexes, wealth itself is not directly measured in the Census and is therefore not included in SEIFA.
  • The remoteness of an area can impact on people's ability to participate in society. Remoteness is not included in 2006 SEIFA.
  • The cost of living within an area impacts on a household's access to economic resources and ability to participate in society. However, the difference in the cost of living between areas is difficult to measure and is not captured in the Census.
  • Much of the information related to socio-economic disadvantage is related to the age of a person, such as income and education. The decision whether to account for age is determined by the particular analysis for which SEIFA is being used, and therefore accounting for age has not been done within SEIFA.(footnote 9) Each user needs to consider whether their particular research should account for age. The decision depends on the particular analysis being undertaken. Please refer to Age Standardisation in the Glossary.
  • There are many other important socio-economic issues which are not measured in the Census, such as health, crime rates, pollution and financial stress.

This information must be included separately in an analysis if considered important.


In addition, there is some information captured by the Census that was not included in SEIFA. There are two reasons why this information was not included. First, a measure that was too closely related to other measures already in SEIFA was dropped from the index. Second, a measure that contributed very little to SEIFA was also dropped from the index. This is explained in more detail in Chapter 3 and in the Technical Paper.


Can I create my own index?


Some users wish to create their own index to use different information to that used in SEIFA. Census information is freely available via CData Online, and the Basic Community Profile Datapack which is available on a cost-recovery basis.(footnote 10) However it is not possible to create a complex index like SEIFA using these products. First, SEIFA is created using unperturbed Census data, whereas these products have been perturbed to protect confidentiality. Second, only a selection of the Census data items are available in these products. Last, as discussed in Chapter 3, the variables used in SEIFA are complex, and variables of this complexity cannot be recreated using these products. More complex variables can be requested through Client Services(footnote 11) , also on a cost-recovery basis. However, this data will also be perturbed.


Some users wish to create their own index to use different areas to that used in SEIFA. As discussed earlier in this chapter, SEIFA indexes are created for five different types of area: Census Districts (CDs), Statistical Local Areas (SLAs), Local Government Areas (LGAs), Postal Areas (POAs) and State Suburbs (SSC). However, you can also use the SEIFA indexes to create scores for other types of area. Because CDs form the basis of all of the ASGC standard geography boundaries, CD scores can be combined to represent larger standard areas. To create a score for a standard area, use a population weighted average of the CDs within the area. Bear in mind that this method changes the distribution of the index. These issues are discussed further in the Glossary (under Population Weighting) and the Technical Paper.


Why do CDs in different deciles have the same score?


The decimal places are not shown for the SEIFA scores as this may imply a level of accuracy that is not provided by a general measure of relative disadvantage like SEIFA. Therefore, some CDs appear to have the same score because the decimal places are not shown, and due to the standard distribution chosen for SEIFA. As discussed earlier, SEIFA scores have been standardised to a mean of 1000 and standard deviation of 100. This means that two-thirds of the CDs, approximately 25,000 CDs, will have a SEIFA score between 900 and 1100. This choice of standard distribution means that some CDs look like they have the same score when the decimal places are not shown. Using the Index of Relative Disadvantage as an example, both Decile 1 and Decile 2 have several CDs with a score of 879. If the standard deviation was instead set to 1000, then these scores would then be 8790, 8791 and so on.


Please refer to Standardisation in the Glossary for more information.


1 http://www.abs.gov.au/ausstats/abs@.nsf/mf/2033.0.55.001 <back
2 2006 SEIFA indexes for CDs, SLAs, LGAs and POAs were released on 26 March 2008, with SSC indexes subsequently released. <back
3 POA and SSC are not part of the Australian Geographic Standard Classification (ASGC). <back
4 For small populations, each person greatly impacts the area's SEIFA score. For example, if there are five people in an area, then each person is equal to 20%. If one person in the area is a 'Manager', then an area with 100 people must have 20 'Managers' to be equivalent. One more 'Manager' would matter a lot to the smaller area, but little to the larger area. These two areas cannot really be compared. <back
5 By definition there will be a relationship between an index and the information that was used to create it. Note however, that the information used to create SEIFA were area-level measures; that is, they were represented as a proportion of people or households within an area. This means that the information used by your analysis may be conceptually different to the information used in SEIFA, if it is a person-level measure for example. This note applies to all the indexes. <back
6 A general measure of disadvantage is not suitable for every analysis. <back
7 The 2006 Index of Economic Resources was created using a different set of variables to those used to create the Index of Education and Occupation. These indexes share one variable, unemployment, however this variable is defined differently to match the concept of each index. However, these indexes are correlated. <back
8 In the same way, the macroeconomy and the global economy can also be relevant to your analysis. <back
9 Adjusting for age was only undertaken for the variable measuring 'need for assistance'. Refer to the Glossary for more detail. <back
10 Another Census product, Table Builder, was not yet available at the time of publication, and is expected to be available on a cost-recovery basis. <back
11 http://www.abs.gov.au/websitedbs/d3310114.nsf/home/Census%20Contacts <back


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