4431.0.55.002 - ABS Sources of Disability Information, 2012 - 2016  
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COLLECTION AND INTERPRETATION OF ABS DISABILITY DATA

Challenges of collecting disability data

Collecting disability data poses particular challenges because of the complex nature of experiences that affect the physical, social and emotional well-being of individuals with disability and their families. The challenges can arise from a number of sources, ranging from the impairment and the respondent’s perception of disability, some are social in nature, some economic and some relate to the way in which the disability information is collected.

From the perspective of the respondent, the subjective and variable nature of some disabilities may mean that responses are affected by factors such as a person's energy levels, optimism, pain or depression at the time of the survey. Similarly, the episodic or seasonal nature of some conditions (e.g. epilepsy, asthma) may mean that they are not causing difficulties at the time of interview and are therefore not reported as causing restrictions.

The fact that a person may have so completely adapted to their disability that they are no longer conscious of an inability to perform certain tasks means they may fail to report limitations associated with the disability.

Social influences on responses can arise because of differing individual perceptions and cultural concepts of what constitutes a difficulty or restriction. There is also the possibility the sensitive nature of the topic which may lead to underreporting of conditions such as alcohol and drug-related conditions, mental illness or mental deterioration and the need for help with personal care activities.

Similarly, there may be a tendency for older people to compare themselves with other older people. Under reporting can occur when people compare their experiences to those of a similar age and either downplay difficulties they may have in comparison, or attribute these difficulties to the effects of old age rather than to the existence of a limitation or disability.

From an economic perspective, over-reporting of disability may occur where people are justifying non-participation in the labour force or feel it will improve their chances of receiving a disability pension. This can be seen in increases in disability support pension applications when the disability pension is more generous than unemployment benefits (Cai & Gregory 2004).

The way in which the data is collected can influence the outcome as well. For example, issues can arise trying to ensure that accurate data are collected when respondents answer on behalf of other people in a household. While the person responding on behalf of another person might be more objective in assessing difficulty and the need for help, they may not be aware of all the conditions the person has or how these affect the person's daily living. Also, while prompt cards reduce the repetition of similar questions and lessen the time taken to collect information, they can also lead to responses that differ from a methodology that asks detailed separate questions about each condition. This is an area where the SDAC and Short Disability Module differ.

    These difficulties increase the variability of disability estimates obtained from the ABS surveys, but every effort is made to minimise their effect. Questionnaires are designed carefully and tested to obtain objective and repeatable responses wherever possible. In particular, terms such as 'disability', which are prone to wide interpretation across the community, are not directly used in questionnaires. Identification of disability is determined from questions that avoid emotive terms and judgements and instead focus on what a person can or cannot do.

    Comparing data across different surveys

    In the ABS, each collection of disability data is based on methodologies unique to the particular survey in which the data was collected. While these methodologies are expected to contribute to differences between the statistics available from the different sources, it is impractical to determine just how much difference is due solely to the collection methodology inferences about an entire population. As each survey draws on a different sample, there can be sampling variation between different surveys, even if the target population is the same. A survey with a larger sample size will generally produce estimates with lower sampling variability than those with smaller sample sizes. For details about the impact of sample size on the variability of estimates, please see the second appendix to this publication.

    ABS Sources of disability data

    Disability information was first collected as a supplementary topic in the Monthly Population Survey (MPS) of 1967 and twice more in the MPS in the 1970s. Over the years since then, the ABS has developed three major disability collections, each conceptually related to the other but distinct in purpose and output. These are the SDAC, the Short Disability Module used in household surveys and the Census.

    Survey of Disability, Ageing and Carers

    The most detailed and comprehensive source of disability data is the Survey of Disability, Ageing and Carers. This survey had its inception as the Survey of Handicapped Persons in 1981 and has been conducted eight times since under various names. One of the main purposes of the SDAC is to collect extensive national and state level data on disability and to provide accurate prevalence rates of disability for Australia. A comparison of the prevalence rates of disability between two SDACs will provide an indication of changes over time. The Survey of Disability, Ageing and Carers, as it has been known since 1993, was last conducted in 2015 and is being conducted again in 2018.

    This large, specialist survey has been developed specifically to align with international measures of disability as described in the International Classification of Functioning, Disability and Health (ICF). It contains 166 questions and is designed to provide a wealth of detail on the identification of disability, its underlying conditions, consequent levels of severity of restriction, participation in education, employment and community services and on the need for, and receipt of, assistance (extended to cover older people without a disability).

    The survey also identifies carers, the nature of their role, their access to support and the impact of the caring role on their lives.

    The survey includes non-private dwellings, with a separate component to collect information from health establishments.

    One of the main purposes of the SDAC is to collect extensive national and state level data on disability and to provide accurate prevalence rates of disability for Australia. It also provides a breakdown of the prevalence of disability by the level of severity, which is outlined in the table below.


    Possible ‘Disability Status’ outputs from SDAC

    1Disability
    11Specific limitation or restriction
    111Core activity limitation
    1111Profound core activity limitation
    1112Severe core activity limitation
    1113Moderate core activity limitation
    1114Mild core activity limitation
    112Education/employment restriction only
    12 No specific limitation or restriction
    2Long-term health condition without disability
    3No disability or long-term health condition



    Significance of the ‘Disability Status’ measure

    Some explanation of the categories in this measure is warranted given that the ABS recommends users of disability data have a thorough understanding of the different sub-populations in the measure and how they relate to each other.

    In the Short Disability Module, responses from several combinations of questions have been used to derive differing levels of disability (derivation is a process of combining responses from a number of questions to create new measures). In total, these levels are referred to as the 'severity of disability' measure and this measure allows for the analyses of the following sub categories:

    a) The SDAC first establishes the presence of any long-term limitations or restrictions. A specific limitation refers to anyone who has either a core activity limitation (see below) or requires extra support for employment (for those aged 15 to 64 years) or education (for those aged 5 to 20 years);

    b) It then ascertains whether any of these restrictions affect a person's ability to care for themselves, to communicate with others or to move around their environs (these three activities are referred to as the 'core activities' of self-care, communication and mobility and are deemed to be essential to normal, everyday living);

    c) It categorises the extent to which a limitation might impact on a person's ability to perform any of the core activities:


      A profound core activity limitation means that a person always needs help with at least one of the core activities;

      A severe core activity limitation means that a person needs help with at least one of the core activities some of the time, has difficulty understanding or being understood by family or friends, or can communicate more easily using sign language or other non-spoken forms of communication;

      A moderate core activity limitation refers to someone who has difficulties with at least one of the core activities, but does not need assistance; and

      A mild core activity limitation refers to someone who uses aids but does not have difficulties with any of the core activities, cannot easily walk 200 metres, cannot walk up and down stairs without a handrail, cannot easily bend to pick up an object from the floor, cannot use public transport, can use public transport, but needs help or supervision or someone who needs no help or supervision, but has difficulty using public transport.


    e) People who have a disability but are not restricted in their ability to perform the core activities and have no employment/schooling restriction are classified as having no specific limitation or restriction;

    f) Finally, the measure includes those with no disability or long term health conditions, allowing for the comparison of people with disability to those without disability.

    These prevalence rates since 1993 are presented in the Table below.


    SDAC Disability Status prevalence rates (Australian population) (%)

    1993
    1998
    2003
    2009
    2012
    2015
    Profound core activity limitation
    2.4
    2.9
    3.0
    2.9
    3.2
    3.1
    Severe core activity limitation
    1.7
    3.2
    3.3
    2.9
    2.9
    2.8
    Moderate core activity limitation
    2.6
    3.5
    3.5
    3.0
    2.8
    2.6
    Mild core activity limitation
    5.3
    5.5
    5.3
    5.6
    6.0
    6.1
    Education/Employment restriction
    2.2
    1.8
    2.0
    1.6
    1.4
    1.5
    No specific limitation of restriction
    3.8
    2.4
    2.9
    2.5
    2.2
    2.3
    Total with disability
    18.0
    19.3
    20.0
    18.5
    18.5
    18.3


    A comparison of results between the different SDACs indicate that the prevalence of disability generally only changes slowly over time. Because of this, it is possible to compare results from other surveys using different measures of disability against the benchmarks set by the SDAC, even though these other surveys may have been conducted in different time periods and show considerable variation in some of their topics.

    Short Disability Module

    There are many social dimensions to the experience of disability. The large number of questions in the SDAC to assess disability levels limits the time in which to ask respondents additional questions about the social and economic context of their lives.

    This is an area of particular interest to users of disability data. As a result, the ABS developed a Short Disability Module in the early 1990s for use in household surveys to investigate disability in relation to social and economic circumstance. Various forms of this module were used from 1992 onwards, with the current standard form of the Short Disability Module, as it has come to be known, first being used in the 2012 Australian Health Survey.

    The Short Disability Module is designed to identify the population with disability within any of the social surveys in which the module has been included. For example, the inclusion of the Short Disability Module in the 2014 General Social Survey, allows for analysis of the social characteristics of people with a disability compared to those without disability. Similarly, the inclusion of the Short Disability Module in the 2014-15 National Health Survey, allows for analysis of health characteristics of people with disability compared with those without disability as well as health risk factors.

    The Short Disability Module applies similar criteria as the SDAC to identify people with a disability and determine their severity of restriction, but uses only 16 questions and a series of prompt cards. The questions used are compatible with the Activities and Participation component of the International Classification of Functioning and are based directly on the questions used in the SDAC.

    The resulting 'Severity of Disability' measure that is associated with the Short Disability Module allows for the following measures to be output and is intended to be broadly comparable to the same concept in the SDAC:


    Possible ‘Severity of Disability’ outputs from Short Disability Module

    1Disability or long-term health condition
    11Specific limitation or restriction
    111Core activity limitation
    1111Profound core activity limitation
    1112Severe core activity limitation
    1113Moderate core activity limitation
    1114Mild core activity limitation
    112Education/employment restriction only
    12 No specific limitation or restriction
    2No disability or long-term health condition


    Significance of the ‘Severity of Disability’ measure

    In the Short Disability Module, responses from several combinations of questions have been used to derive differing levels of disability (derivation is a process of combining responses from a number of questions to create new measures). In total, these levels are referred to as the 'severity of disability' measure and this measure allows for the analyses of the following sub categories:

    a) The Short Disability Module first establishes the presence of any long-term health conditions;

    b) It then determines if any of these health conditions cause specific limitations or restrictions. A specific limitation refers to anyone who has either a core activity limitation (see below) or requires extra support for employment (for those aged 15 to 64 years) or education (for those aged 5 to 20 years);

    c) It then ascertains whether any of these restrictions affect a person's ability to care for themselves, to communicate with others or to move around their environs (these three activities are referred to as the 'core activities' of self-care, communication and mobility and are deemed to be essential to normal, everyday living);

    d) It categorises the extent to which a limitation might impact on a person's ability to perform any of the core activities:
      A profound core activity limitation means that a person always needs help with at least one of the core activities;
      A severe core activity limitation means that a person needs help with at least one of the core activities some of the time. This differs from SDAC in that more details about communication impairments are collected in the SDAC and factor into the classification of the severity of the disability (such as the use of non-verbal languages);
      A moderate core activity limitation refers to someone who has difficulties with at least one of the core activities, but does not need assistance; and
      A mild core activity limitation refers to someone who uses aids but does not have difficulties with any of the core activities. In the SDAC people are explicitly asked about the use of hearing aids for inclusion in this category, but they are not in the Short Disability Module.

    e) People who have a disability but are not restricted in their ability to perform the core activities and have no employment/schooling restriction are classified as having no specific limitation or restriction;

    f) Finally, the measure includes those with no disability or long term health conditions, allowing for the comparison of people with disability to those without disability.

    The questions and prompt cards used in the Short Disability Module are listed in the fourth appendix, which also shows how these questions are used to classify people according to the 'Severity of Disability' standard. Even though the same questions are used to measure disability in different social surveys (such as the NHS and the SIH), there are pertinent factors to bear in mind which all have a subtle effects on the final data collected when comparing data across multiple surveys. These include: the number of people interviewed; the placement of the questions within the survey; and the use of proxy interviews (where someone answers on behalf of another person who is unable to answer for themselves).

    Census of Population and Housing

    The Census of Population and Housing enables the production of detailed regional data to aid in the development and monitoring of state and Federal government policies and to inform the allocation of service delivery to small population groups. The provision of disability services through the different levels of government and the involvement of non-profit and commercial organisations in service provision drive demand for small area data. Although the SDAC provides the best quality disability information from surveys in Australia and the Short Disability Module provides a good range of demographic data as sample surveys they cannot provide reliable data at the small geographic level or for small populations of interest.

    In response to this need for small area data which would allow the ability to examine the characteristics of small populations, a measure of disability was developed for use in the 2006 Census of Population and Housing. It contained 4 questions and was designed to be both conceptually comparable to the SDAC and practical for use in a national Census. It was agreed that the Census questions be based on the SDAC concept of 'Profound or severe core activity limitation', the population for whom service delivery has the most consequence. Testing of the new questions indicated that the data would be of an acceptable quality for use as an indicator of the target population. As a result, the 2006 Census produced the first Census output of information on people with a 'Need for assistance' and the questions were subsequently used in Census 2011 and 2016.

    Four questions were asked in the Census to identify people who had need for assistance with one of the core activity areas of self-care, communication or mobility because of a disability, long term health condition or the effects of old age. Three of these questions related to the existence of a need for assistance in one of the core activities, and the fourth question identified the reasons as to why this assistance was necessary.

    The questions used in the Census and the derivation from these questions to determine whether a person had a need for assistance are presented in the fifth appendix. Detailed information on the "Core Activity Need for Assistance" data item is included in the information paper Disability Variables, 2006 (cat. no 1200.0.55.001).


    All the ABS collections which have included disability measures are listed in the sixth appendix to this publication.

    Analysis in this information paper only makes reference to the most recent of these surveys, excluding the Aboriginal and Torres Strait Islander surveys which are to be covered in a separate, forthcoming comparative analysis of disability measures by Indigenous/non-Indigenous status.

    Washington Group Short Set

    The final source of disability data collected by the ABS is the Washington Group Short Set. The Washington Group (WG) is a United Nations Statistics Commission City Group formed of representatives of national statistical offices working on developing methods to better improve statistics on persons with disabilities globally, with input from various international agencies and experts. As part of their work, they developed a short set of six questions aimed at identifying people with disabilities.

    The ABS used the WG Short Set of Questions in the 2016 Supplementary Disability Survey (SDS). The 2016 SDS was conducted as a consultancy service for the Australian Department of Foreign Affairs and Trade and is not, at this stage, expected to be repeated. Details can be found in Supplementary Disability Survey, 2016 (cat.no 4450.0). See also Research Paper: Analysis of the 2016 Supplementary Disability Survey, 2016 (cat.no. 4450.0.55.001) for detailed analysis of the SDS results and the relationship with the ABS 2015 Survey of Disability Ageing and Carers. This data has not been included in the analyses following as the ABS does not currently intend repeating the SDS.