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6 The survey also collected a small amount of information about people not in the target populations, allowing for comparison of demographic and socio-economic characteristics of the target populations with the general population.
SCOPE OF THE SURVEY
7 The scope of SDAC was persons in both urban and rural areas in all states and territories, living in both private and non-private dwellings (including persons in cared-accommodation), but excluding:
9 The coverage of SDAC was the same as the scope except that the following (small) populations were not enumerated for operational reasons:
11 Usual residents of selected private dwellings and non-private dwellings (excluding persons in cared-accommodation) were included in the survey unless they were away on the night of enumeration and were likely to be away for the remainder of the enumeration period. This was designed to avoid multiple selection of a person who might be spending time, for instance, in a short-term caravan park, and be eligible for selection there and at their usual residence.
12 Visitors to private dwellings were excluded from coverage as the expectation was that most would have their chance of selection at their usual residence.
13 Occupants of cared-accommodation establishments in the scope of the survey were enumerated if they had been, or were expected to be, a usual resident of an establishment for three months or more.
2. SURVEY DESIGN AND OPERATION
1 Multi-stage sampling techniques were used to select the sample for the survey. After sample loss, the household sample included approximately 27,400 private dwellings and 500 non-private dwellings, while the cared-accommodation sample included approximately 1,000 health establishments.
2 After exclusions due to scope and coverage, the final combined sample was 79,164 persons, comprised of 68,802 persons from the household component and 10,362 persons from the cared-accommodation component.
3 The private dwelling sample was chosen using an area based selection methodology, to ensure that all sections of the population living within the geographic scope of the survey were represented. The following steps were undertaken to determine the sample:
5 Similar to the private dwelling selection process, the list of non-private dwellings was first amended to meet the scope and coverage requirements of the survey. The sample was then chosen from a list, which excluded dwellings in very remote areas, collection districts containing a discrete Aboriginal or Torres Strait Islander community, boarding schools, gaols and correctional institutions.
6 Where a non-private dwelling formed part of a group of dwellings, such as within a caravan park, each dwelling was given an equal chance of selection. This was achieved through ordering the dwellings within the group and applying a random selection technique.
7 The sample of non-private dwellings within cared-accommodation establishments was chosen separately from the sample of households. A frame was developed, including all Australian businesses who may provide adequate facilities to support long-term cared-accommodation.
8 A census was then conducted on the frame to determine in-scope businesses; those establishments who provide long-term cared-accommodation. This process is explained further in Data Collection for the cared-accommodation component.
9 Each in-scope establishment was given a chance of selection proportional to the average number of persons it accommodated. In order to identify the occupants to be included in the survey, they were ordered by the respondent (a representative of the business) and a random selection technique was applied.
10 Similar to the 2003 and 2009 surveys, the 2012 survey collected information about people living in households as well as those in cared-accommodation to ensure the survey represented a comprehensive picture of disability in Australia. This was achieved by conducting the survey in two separate parts: the household component and the cared-accommodation component, using different methods for data collection and processing.
11 The household component covered persons in:
13 In this publication, persons in the household component of the survey are referred to as 'living in households'.
14 The cared-accommodation component covered residents of hospitals, nursing homes, hostels and other homes, who had been, or were expected to be, living there or in another health establishment for three months or more.
15 Data for the household component of the survey were collected by trained interviewers, who conducted computer-assisted personal interviews.
16 Households containing people with disability or those aged 65 years and over, were determined through a series of screening questions asked of a responsible adult in the selected household.
17 Households containing people who were carers of persons with a core activity limitation, living either in the same household or elsewhere, or who provided any care to persons living elsewhere, were identified using two methods:
23 The cared-accommodation component was enumerated in two stages using a mail-based methodology directed to administrators of selected health establishments.
24 The first stage involved a census of all known health establishments in Australia. These businesses were sent an approach letter from the ABS, detailing their selection and the requirement for a suitable employee of their establishment to complete a web-based Contact Information Form. This form collected the name and role of a contact officer for the establishment, whether the establishment offered cared-accommodation to occupants on a long-term basis (i.e. for a period of three months or more), the current number of occupants within the cared-accommodation component, and the type of establishment.
25 The second stage was based on a sample of the health establishments that indicated their ability to provide long-term cared-accommodation in stage one. Each establishment was given a likelihood of selection relative to the number of long-term occupants they had reported. If a health establishment was selected, the nominated contact officer was required to select a sample of occupants in their establishment, following the instructions provided. The contact officer then completed a separate questionnaire for each selected occupant.
26 The range of data collected in the cared-accommodation component was narrower than in the household component as some topics were not suitable for collection through a proxy or were irrelevant to those residing in cared-accommodation.
3. DATA QUALITY
1 A number of editing techniques were implemented within the computer-assisted survey instrument to assist with processing data collected by the personal interviews, such as:
2 The majority of reported long-term health conditions were automatically coded to a list of approximately 1000 health conditions, within the computer-assisted personal interview. Those conditions that could not be automatically coded at the time of data collection were reviewed on a case by case basis by ABS employees during post-collection editing.
3 The code list used for the 2012 SDAC was similar to that used in previous surveys, with some minor updates. Conditions classified at the full level of detail are not generally available for output from the survey, however, they can be regrouped in various ways for output. The output classification, developed for the SDAC, is based on the International Classification of Diseases: 10th Revision (ICD-10). For a concordance of codes used in the 2012 SDAC with the ICD-10 please refer to the Long-term Health Conditions spreadsheet available in the the Downloads tab.
4 An extensive range of edits and quality checks were performed on the aggregated data file, after the completion of data collection. These included:
WEIGHTING, BENCHMARKING AND ESTIMATION
5 Weighting is the process of adjusting results from a sample survey to infer results for the total population. To do this, a 'weight' is allocated to each enumerated person. The weight is a value which indicates how many population units are represented by the sample unit.
6 The first step in calculating weights for each person is to assign an initial weight, which is equal to the inverse of the probability of being selected in the survey. For example, if the probability of a person being selected in the survey was 1 in 300, then the person would have an initial weight of 300 (that is, they represent 300 people).
7 The responses from persons in the cared-accommodation component and persons in the private dwelling and non-private dwelling (other than cared-accommodation) components of the survey were weighted together in order to represent the entire in-scope population.
8 The weights were calibrated to align with independent estimates of the population, referred to as benchmarks, in designated categories of sex by age by area of usual residence. Weights calibrated against population benchmarks ensure that the survey estimates conform to the distribution of the population rather than to the distribution within the sample itself. Calibration to population benchmarks helps to compensate for over or under-enumeration of particular categories of persons which may occur due to either the random nature of sampling or non-response.
9 The survey was benchmarked to the estimated resident population (ERP) in each state and territory, excluding those living in very remote areas of Australia and those living in a collection district in a non-very remote area containing one or more discrete Aboriginal or Torres Strait Islander communities, at 30 October 2012. The SDAC estimates do not (and are not intended to) match estimates for the total Australian population obtained from other sources (which may include persons living in very remote parts of Australia and persons living in collection districts that contain one or more discrete Aboriginal or Torres Strait Islander communities).
10 Survey estimates of counts of persons are obtained by summing the weights of persons with the characteristic of interest. Estimates of non-person counts (e.g. days away from work) are obtained by multiplying the characteristic of interest with the weight of the reporting person and aggregating.
11 Totals presented in Tables 1 and 2 comparing rates over time are shown as age-standardised percentages. Age standardisation has been undertaken using the direct method (see Technical Note). An age-standardised rate removes the effects of different age structures when comparing population groups or changes over time. A standard age composition is used, in this case the age composition of the 30 June 2001 ERP. The standardised rate is that which would have prevailed if the actual population had the standard age composition. Age-specific disability rates are multiplied by the standard population for each age group. The results are added and the sum calculated as a percentage of the standard population total to give the age-standardised rate. The standardised rates should only be used to identify differences between population groups and changes over time.
12 In accordance with the Census and Statistics Act, 1905, all published estimates are subjected to a confidentiality process before release. This process is undertaken to minimise the risk of identifying particular individuals, families, households or dwellings in aggregate statistics, through analysis of published data.
13 To minimise the risk of identifying individuals in aggregate statistics, a technique is used to randomly adjust cell values. This technique is called perturbation. Perturbation involves small random adjustment of the statistics and is considered the most satisfactory technique for avoiding the release of identifiable statistics while maximising the range of information that can be released. These adjustments have a negligible impact on the underlying pattern of the statistics.
14 After perturbation, a given published cell value will be consistent across all tables. However, adding up cell values to derive a total will not necessarily give the same result as published totals. The introduction of perturbation in publications ensures that these statistics are consistent with statistics released via services such as TableBuilder. Refer to paragraphs 14 and 15 of the Interpreting the Results chapter for a further illustration of how perturbed estimates will be published.
RELIABILITY OF ESTIMATES
15 All sample surveys are subject to sampling and non-sampling error.
16 Sampling error is a measure of the variability that occurs by chance because a sample, rather than the entire population, is surveyed. Since the estimates in this publication are based on information obtained from occupants of a sample of dwellings they are subject to sampling variability; that is they may differ from the figures that would have been produced if all dwellings had been included in the survey. For more information refer to the Technical Note.
17 Non-sampling error may occur in any data collection, whether it is based on a sample or a full count such as a census. Non-sampling errors occur when survey processes work less effectively than intended. Sources of non-sampling error include non-response, errors in reporting by respondents or in recording of answers by interviewers, and occasional errors in coding and processing data.
18 Non-response occurs when people cannot or will not cooperate, or cannot be contacted. Non-response can affect the reliability of results and can introduce a bias. The magnitude of any bias depends on the rate of non-response and the extent of the difference between the characteristics of those people who responded to the survey and those who did not.
19 The following methods were adopted to reduce the level and impact of non-response:
THE OUTPUT FILE
21 To produce tabular estimates and other outputs from the collected data, information from the survey was stored on an output file in the form of data items. In some cases, items were formed directly from information recorded in individual survey questions, in others, data items were derived from answers to several questions (e.g. the item ‘disability status’ is derived from responses to approximately 80 questions).
22 In designing the output data file, the aim was to create a file that was similar to the 2009 data file. The result is a ten level hierarchical output file, the structure of which is as follows:
24 Data about households and families are contained as individual characteristics on person records. A full listing of output data items available from the survey can be accessed on the ABS web site, under the Downloads tab of this release.
4. INTERPRETING THE RESULTS
INTERPRETATION OF RESULTS
1 Disability is a difficult concept to measure because it depends on a respondent's perception of their ability to perform a range of activities associated with daily living. Factors discussed below should also be considered when interpreting the estimates contained in this publication.
2 Information in the survey was based, wherever possible, on the personal response given by the respondent. However, in cases where information was provided by another person, some answers may differ from those the selected person would have provided. In particular, interpretation of the concepts of 'need' and 'difficulty' may be affected by the proxy-interview method.
3 A number of people may not have reported certain conditions because of:
5 The need for help may have been underestimated as some people may not have admitted needing help because of such things as a desire to remain independent, or may not have realised help was needed with a task because help had always been received with that task.
6 The criteria by which people assessed whether they had difficulty performing tasks may have varied. Comparisons may have been made with the ability of others of a similar age, or with the respondent's own ability when younger.
7 The criteria used to identify disability and disability status has not changed between 2009 and 2012.
8 The different collection methods used (personal interview for households, and administrator completed forms for cared-accommodation) may have had some effect on the reporting of need for assistance with core activities. As a result there may have been some impact on measures such as disability status. If so, this would have more impact on the older age groups because of their increased likelihood of being in cared-accommodation.
Primary carer completion of the self-enumeration form
9 In this survey, persons who confirmed they were the primary carer of a person with disability were also asked to complete a self-enumeration form which asked questions relating to their attitudes to, and experience of, their caring role. Self-enumeration is seen as the most appropriate method of achieving response to these topics, due to the personal nature of the questions.
10 Some data items in this publication, which relate to primary carers, are derived from questions answered in the self-enumeration form. In 2012, these forms had moderately high levels of non-response, described as the 'not stated' population. This represented approximately 25% of the estimated population of primary carers.
11 Non-response introduces the potential for bias if those who did respond were inherently different to the total population of primary carers. However, analysis of 2012 data showed there were no substantial differences between the characteristics of primary carers who responded and all primary carers. For further information on survey non-response see paragraphs 15 to 20 in the Data Quality chapter of the Explanatory Notes.
12 In this publication, 'not stated' responses have been excluded from both the numerator and the denominator for items derived from the primary carers' self enumeration form. Proportions have been calculated excluding these 'not stated' responses. Users should take this into consideration when reviewing output derived from the self-enumeration form.
Northern Territory estimates
13 Changes to the scope of this survey from 2009 to 2012 will impact estimates for the Northern Territory. The amended scope is described in the Survey Overview chapter of the Explanatory Notes (paragraphs 7 and 8). Households in excluded ICF CDs contribute to around 10% of Northern Territory households, as such, estimates in the 2012 publication are not comparable to the 2009 survey. Estimates displayed as proportions are comparable with previous surveys.
Adjustment of estimates
14 The random adjustment of estimates, by perturbation, for the purpose of maintaining confidentiality, may result in the sum of components not equalling the total, or subtotal. In these cases, the difference between the sum of components and its total will be small and will not impact the overall information value of the estimate for the total or any individual component. Where a footnote is not included on an estimated total, it should be assumed that any discrepancy between the total and the sum of its components is due to the effects of rounding or perturbation.
15 In some instances it is expected that a published total will not equal the sum of its components. For example:
16 Long-term health conditions described in this publication were categorised to an output classification developed for the SDAC, based on the International Classification of Diseases: 10th Revision (ICD-10). For a concordance of codes used in the 2012 SDAC with the ICD-10 please refer to the Long-term Health Conditions spreadsheet on the Downloads tab. This classification, with some minor amendments, has been used for the 2003, 2009 and 2012 surveys.
17 Country of birth was classified according to the Standard Australian Classification of Countries, Second edition, 2008 (cat. no. 1269.0).
18 Main language spoken at home was classified according to the Australian Standard Classification of Languages, 2005-06 (cat. no. 1267.0).
19 Education data were classified according to the Australian Standard Classification of Education (ASCED), 2001 (cat. no. 1272.0).
20 Similar to previous collections of the SDAC, remoteness areas were classified according to the Statistical Geography: Volume 1 - Australian Standard Geographical Classification (ASGC), 2006 (cat. no. 1216.0).
21 For the 2012 survey, an approximate concordance is available to the more recent Australian Statistical Geography Standard (ASGS): Volume 1 - Main Structure and Greater Capital City Statistical Areas, 2011 (cat. no. 1270.0.55.001).
Socio-economic Indexes for Areas (SEIFA)
22 Socio-economic Indexes for Areas (SEIFA) is a suite of four summary measures that have been created from 2011 Census information. Each index summarises a different aspect of the socio-economic conditions of people living in an area. The indexes provide more general measures of socio-economic status than is given by measures such as income or unemployment alone.
23 SEIFA uses a broad definition of relative socio-economic disadvantage in terms of people's access to material and social resources, and their ability to participate in society. While SEIFA represents an average of all people living in an area, it does not represent the individual situation of each person. Larger areas are more likely to have greater diversity of people and households.
24 For more detail, see the Census of Population and Housing: Socio-Economic Indexes for Areas (SEIFA), Australia, 2011 (cat. no. 2033.0.55.001).
25 Following the adjustment of estimates through perturbation, the estimates presented in this publication have been rounded. As a result, sums of components may not add exactly to totals.
26 Proportions presented in this publication are based on unrounded figures. Calculations using rounded figures may differ from those published.
MAKING COMPARISONS BETWEEN SURVEYS OVER TIME
27 Much of the content of the seven disability surveys conducted by the ABS in 1981, 1988, 1993, 1998, 2003, 2009 and 2012 is comparable. There are differences, however, as later surveys have attempted to obtain better coverage of disability and of specific tasks and activities previously considered too sensitive for a population survey. A full listing of output data items available from the 2012 survey can be accessed on the ABS web site, under the Downloads tab of this release.
Changes between surveys
Identification of the primary carer population
28 Prior to determining a primary carer, this survey identifies those people who provide the most informal assistance to someone else, based on responses provided by either the responsible adult responding for the household or the recipient of care. These people are known as 'possible primary carers'. Possible primary carers are only confirmed as primary carers if they complete an interview, in person or by proxy, and meet the following criteria:
30 In 2012, the identification process for possible primary carers changed to only require a carer to provide the most informal assistance for core activities overall, regardless of whether they were the secondary provider of this assistance. This change was found to increase the number of possible primary carers identified, however the overall number of primary carers identified was not affected.
Older persons aged 65 years and over
31 In 2012, the definition of an older person changed to 65 years and over, from 60 years and over in the 2009 survey. The increase of age for older persons was driven by social factors such as increases in life expectancy and changes to aged care policy and the retirement age.
32 In 2012, some existing data items were updated to improve output quality, consistency with other ABS surveys and to reflect changes in survey design. The following modules changed significantly between the 2009 and 2012 surveys. In some instances, these changes may impact upon the comparability of data items across previous surveys.
33 In 2012, a number of new questions and survey modules were included in the household questionnaire. The new output items produced from these questions are detailed by topic, as follows.
Computer and internet use
Feelings of safety
Satisfaction with the range of disability service options and the quality of support received
5. SURVEY OUTPUT AND DISSEMINATION
1 It is planned that results from the 2012 SDAC will be available in the form of:
2 A sub-set of tables in a spreadsheet format similar to those in this publication will be produced for each state and territory (subject to standard error and confidentiality constraints and excluding time series tables). These tables will be available from the ABS website <www.abs.gov.au> from March 2014 under the Disability, Ageing and Carers: Summary of Findings, 2012 publication (cat. no. 4430.0).
3 It is expected that a basic confidentialised unit record file (CURF) and Table Builder will be produced from the SDAC, subject to the approval of the Australian Statistician. The basic CURF will be available via CD ROM or Remote Access Data Laboratory (RADL) and the Table Builder will be accessible via the ABS website, using a secure log-on portal.
4 A set of themed publications will be released progressively from February 2014, using data from the 2012 SDAC.
5 As well as releasing publications and standard products, the ABS can make available special tabulations, on request and with an associated fee.
6 The Summary of Findings, these Explanatory Notes and the media release are available free of charge on the ABS website <www.abs.gov.au>.
7 ABS publications draw extensively on information provided freely by individuals, businesses, governments and other organisations. Their continued cooperation is very much appreciated; without it, the wide range of statistics published by the ABS would not be available. Information received by the ABS is treated in strict confidence as required by the Census and Statistics Act, 1905.
8 Previous ABS publications relating to disability, ageing and carers:
Disability, Ageing and Carers: User Guide, Australia, 2009 (cat. no. 4431.0.55.001)
Disability, Ageing and Carers, Australia: Summary of Findings, 2009 (cat. no. 4430.0)
Disability, Australia, 2009 (cat. no. 4446.0)
Profiles of Disability, Australia, 2009 (cat. no. 4429.0)
Caring in the Community, 2009 (cat. no. 4436.0)
A Profile of Carers in Australia, 2008 (cat. no. 4448.0)
People with a Need for Assistance - A Snapshot, 2006 (cat. no. 4445.0)
9 Other ABS publications which may be of interest include:
Australian Social Trends (cat. no. 4102.0)
Labour Force, Australia (cat. no. 6202.0)
Australian Health Survey: Updated Results, 2011-2012 (cat. no. 4364.0.55.003)
Household Income and Income Distribution, Australia, 2011-2012 (cat. no. 6523.0)
Private Hospitals, Australia, 2011-2012 (cat. no. 4390.0)
General Social Survey: Summary Results, Australia, 2010 (cat. no. 4159.0)
National Aboriginal and Torres Strait Islander Social Survey, 2008 (cat. no. 4714.0)
Census of Population and Housing, 2011
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