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The survey was dependent on the high level of cooperation received from Aboriginal and Torres Strait Islander people and their communities. Without their continued cooperation, the wide range of Aboriginal and Torres Strait Islander statistics published by the Australian Bureau of Statistics (ABS) would not be available.
The ABS is committed to using data to focus on the stories of Aboriginal and Torres Strait Islander people. For this reason, the ABS has not included comparisons with the non-Indigenous population in the narrated summaries and data highlights.
Users who require non-Indigenous comparisons can access information in some data cubes that have been published with age standardised proportions for both the non-Indigenous and Aboriginal and Torres Strait Islander populations. These are available on the Downloads tab. For further information, see Non-Indigenous comparisons (appendix).
HOW THE DATA IS COLLECTED
The survey was developed in conjunction with numerous stakeholders, including representatives from Australian Government agencies, state/territory government agencies, non-government organisations, and academic and research institutions.
A dress rehearsal was conducted in non-remote and remote areas of Western Australia and the Northern Territory in October 2017 to test survey content and procedures.
The range of topics identified for possible inclusion exceeded the capacity of the survey. With the assistance of the advisory groups, these were assessed and priorities were established. Topics ultimately selected for inclusion were those identified as highest priority and which could be appropriately addressed in a survey of this type.
Scope and coverage
The scope of the survey was all Aboriginal and Torres Strait Islander people living in private dwellings.
The following people were not included in the survey:
Coverage exclusions apply to those people who were in scope for the survey, but who were not included in the sampling frame. The following coverage exclusions were applied:
The overall coverage of the 2018–19 NATSIHS was approximately 33% of Aboriginal and Torres Strait Islander persons in Australia. The final sample has been weighted to population benchmarks which align with the scope of the survey to account for undercoverage. Refer to the Non-sampling error and undercoverage section below for more information.
The benchmarks are based on the most recently released Aboriginal and Torres Strait Islander estimated resident population (ERP), with an adjustment to account for the time period of the survey. For more information on ERP, see Estimates of Aboriginal and Torres Strait Islander Australians, June 2016 (cat. no. 3238.0.55.001).
As at 30 June 2016, the estimated resident Aboriginal and Torres Strait Islander population living in private and non-private dwellings was 798,365. Excluding persons in non-private dwellings, the projected Aboriginal and Torres Strait Islander population at 31 December 2018 was 814,013 and this is the population benchmark that the survey results were weighted to meet.
The survey was designed to produce reliable estimates for the whole of Australia, for each state and territory and for remoteness areas. The sample was designed to achieve a Relative Standard Error of less than 25% for key variables.
The survey sample had two parts:
Each part used a multi-stage sampling process to ensure the representativeness of the final sample.
As with previous ABS Aboriginal and Torres Strait Islander surveys, additional sample was collected in the Torres Strait Area, to ensure data of sufficient quality would be available for the Torres Strait Area and the remainder of Queensland.
The community sample was a random selection of discrete Indigenous communities and outstations in non-remote and remote areas.
Dwellings in the non-community sample were selected using a multi-stage area sample.
Number of people selected per household
Within each identified Aboriginal and Torres Strait Islander household in both the community and non-community sample:
Fully or adequately responding households
A fully responding household is one in which all parts of the interview were completed for all persons in scope.
An adequately responding household is the same as a fully responding household, but with legitimate ‘don't know’ answers or refusals where permitted in the survey. For example, adequately responding households include people who declined to answer the substance use questions or have their height, weight, waist circumference or blood pressure measured by an interviewer.
For information on sample counts and response rates, see Response rates, sample counts and estimates (appendix).
Information was collected by trained ABS interviewers using a computer based questionnaire. Prior to enumeration, interviewers:
Interviewers conducted face-to-face interviews in all selected households.
A person aged 18 years or over was asked to provide basic information for all usual residents of the household, including Indigenous status, age, sex and relationships. This person, known as the household spokesperson, answered financial and housing questions, such as income, tenure arrangements and household facilities.
Personal interviews were then conducted with selected Aboriginal and Torres Strait Islander persons aged 15 years and over. Some people were unable to be interviewed because of:
For selected persons aged 15–17 years:
An adult was asked to respond on behalf of children aged less than 15 years.
Use of local Aboriginal and Torres Strait Islander advisors
In communities, interviewers were accompanied, where possible, by local Aboriginal and Torres Strait Islander advisors who assisted in conducting interviews. The advisors:
Variations in data collection and survey questions
To take account of language and cultural differences, the collection method and survey questions sometimes varied in remote areas.
This means some data items are not available for the total Aboriginal and Torres Strait Islander population. Further information on the availability of data items can be found in the Data Item List, available on the Downloads tab.
In non-community areas, where a person selected in the survey initially refused to participate, a follow up letter was sent and a second visit was made (where possible) to encourage participation. There was no follow up of refusals in communities.
HOW THE DATA IS PROCESSED
As only a sample of people were surveyed, their results needed to be converted into estimates for the whole population. This was done with a process called weighting.
For the person level weights, 250 replicate weights were produced to ensure accurate estimates of the standard errors.
After calculating the initial person weights, an adjustment was incorporated into the weighting for persons and households to account for Aboriginal and Torres Strait Islander persons not covered by the sample.
The person and household level weights were separately calibrated to independent estimates of the in scope population, referred to as ‘benchmarks’. The benchmarks used additional information about the population to ensure that:
For this survey, person weights were simultaneously calibrated to the following population benchmarks:
The survey was benchmarked to the estimated Aboriginal and Torres Strait Islander resident population living in private dwellings at 31 December 2018. As people in non-private dwellings (e.g. hotels) are excluded from the scope of the survey, they have also been excluded from the survey benchmarks. Therefore, the 2018–19 estimates do not, and are not intended to, match estimates for the total resident Aboriginal and Torres Strait Islander population obtained from other sources. This approach is consistent with the 2012–13 NATSIHS and 2014–15 NATSISS.
For household weights, the ABS does not produce counts of Aboriginal and Torres Strait Islander dwellings and, as a result, household level benchmarks are not available. Instead, household level weights for this survey were derived from person level benchmarks, consistent with the approach for the 2012–13 NATSIHS and 2014–15 NATSISS. This was done by:
The resulting weight was the final household weight.
Age standardisation is a technique used to enhance the comparability of rates between populations with different age structures. This technique is often used to make comparisons between the non-Indigenous and Aboriginal and Torres Strait Islander populations. For further information, see Non-Indigenous comparisons (appendix).
Two types of error affect the accuracy of sample surveys: sampling and non-sampling error.
Sampling error is the difference between:
The size of the sampling error can be measured. It is reported as the Relative Standard Error (RSE) and 95% Margin of Error (MOE). For more information see the Technical note.
In this publication, estimates with a RSE of 25% to 50% were flagged to indicate that the estimate has a high level of sampling error, and should be used with caution. Estimates with a RSE over 50% were also flagged and are generally considered too unreliable for most purposes.
Margins of Error are provided for proportions to help people using the data to assess how reliable it is. The proportion combined with the MOE shows the range likely to include the true population value with a given level of confidence. This is known as the confidence interval. People using the data need to consider this range if they are making decisions based on the proportion.
Analysis was done to compare the characteristics of respondents to the 2018–19 NATSIHS with a number of data sources to determine data consistency. Some sources for comparison included the:
Estimates presented in this publication have been rounded. As a result, sums of components may not add exactly to totals.
Non-sampling error and undercoverage
Undercoverage is one potential source of non-sampling error. It is the shortfall between the population represented by the achieved sample and the in-scope population. It can introduce bias into the survey estimates; however, the extent of any bias depends on the size of the undercoverage as well as the difference in the characteristics of those people in the coverage population and those of the in-scope population.
Undercoverage rates can be estimated by calculating the difference between the sum of the initial weights of the sample and the population count. If a survey has no undercoverage, then the sum of the initial weights of the sample would equal the population count (ignoring small variations due to sampling error).
In the 2018–19 NATSIHS, there was an increase in the undercoverage rate compared with previous ABS Aboriginal and Torres Strait Islander surveys. The overall 2018–19 NATSIHS undercoverage rate was approximately 67% of the in-scope population at the national level. The estimated undercoverage in both the 2012–13 NATSIHS and the 2014–15 NATSISS was 62%.
The overall undercoverage rate for non-community areas was 68% and for community areas was 57%. The undercoverage rate varied across the states and territories.
Undercoverage rate in National Aboriginal and Torres Strait Islander Health Surveys, by state/territory
Given the high undercoverage rate in the 2018–19 NATSIHS, there was extensive analysis undertaken to ensure the results were consistent with other data sources. Potential bias due to undercoverage was addressed by the application of adjustments to the initial weights and through the use of population benchmarks.
Undercoverage may occur due to a number of factors, including:
Each of the factors is explained in more detail below.
Similar to the 2012–13 NATSIHS and 2014–15 NATSISS, frame exclusions were incorporated to make the sample design more efficient. Part of the frame exclusion that could be contributing to undercoverage are people who may have moved since the 2016 Census of Population and Housing.
Non-response may occur when people cannot or will not cooperate, or they cannot be contacted. The loss of information on persons and households reduces the sample and increases both sampling error and the likelihood of incurring response bias.
Non-response in this survey includes non-response to:
To reduce non-response, the following methods were used:
Of the households screened in non-community areas, 77% of households responded. Of those households who responded to the screening question, 3.9% were identified as having an Aboriginal or Torres Strait Islander usual resident. Of these identified households, 73% then responded to the survey.
In discrete Indigenous communities 74.6% of selected in-scope households responded to the survey.
People not identifying as being of Aboriginal and/or Torres Strait Islander origin
Some Aboriginal and Torres Strait Islander households may not have been identified during the screening process due to:
There was a large increase in the number of people identifying as being of Aboriginal and/or Torres Strait Islander origin between the 2011 and 2016 Censuses of Population and Housing, and these people may not have chosen to identify in the same way for the 2018–19 NATSIHS for various reasons. Data from the 2016 Census is part of the population benchmarks used in this survey. For more information about the change across the Censuses, please refer to Census of Population and Housing: Understanding the Increase in Aboriginal and Torres Strait Islander Counts, 2016 (cat. no. 2077.0).
Issues arising in the field
Known undercoverage due to other issues arising in the field included sample being excluded due to:
The data was collected from July 2018 to April 2019 which may not be fully representative of other time periods in the year. For example, people were asked about the number of times they had consulted with a health professional in the two weeks prior to interview. Travel to access health care facilities, particularly in remote areas, may be subject to seasonal variation throughout the year. Results could have differed if the survey had been conducted over the whole year or in a different part of the year.
HOW THE DATA IS RELEASED
The published results of the 2018–19 NATSIHS include a summary of findings and data cubes presented in spreadsheet format.
A copy of the survey questionnaire, prompt cards and the physical measurements card provided to respondents are available on the Downloads tab.
Additional data from the survey will be available via a range of other products and services:
To support the return of results to Aboriginal and Torres Strait Islander peoples, a series of thematic releases are planned for distribution to Aboriginal and Torres Strait Islander communities.
For further information on the comparability of data items see the Downloads tab.
The Census and Statistics Act 1905 authorises the ABS to collect statistical information, and requires that information is not published in a way that could identify a particular person or organisation. The ABS must make sure that information about individual respondents cannot be derived from published data.
The ABS takes care in the specification of tables to reduce the risk of identifying individuals. Random adjustment of the data is considered the best way to do this. A technique called perturbation randomly adjusts all cell values to prevent identifiable data being exposed. These adjustments result in small introduced random errors, which often result in tables not being 'internally consistent' (that is, interior cells not adding up to the totals). However, the information value of the table as a whole is not impacted. This technique allows the production of very large/detailed tables valued by clients even when they contain cells of very small numbers.
In this publication, perturbation was applied to published data from 2018–19 onwards. Data from surveys before 2018–19 have not been perturbed, but have been confidentialised by suppressing cells if required.
INTERPRETATION OF RESULTS
Care has been taken to ensure that the results of this survey are as accurate as possible. The following factors should be considered when interpreting these estimates.
For a number of survey data items, some people were unwilling or unable to provide the required information.
Information was collected for children aged 0–3 years (that is, children up to 3 years and 11 months of age, also referred to as 0–47 months).
A chronic condition is a long-term health condition selected for reporting in this survey because it is common, poses significant health problems, has been the focus of population health surveillance efforts, and action can be taken to prevent its occurrence.
A person has a disability or restrictive long-term health condition if they have a limitation, restriction, impairment, disease or disorder which restricts their everyday activities and has lasted, or is expected to last, for at least six months.
A person with a disability or restrictive long-term health condition is further classified by:
A person has a specific limitation with a core activity if they need help from another person, have difficulty or use an aid or other equipment to perform at least one selected task. The level of limitation for each core activity is based on the amount of help a person needs with a selected task:
A person's overall level of core activity limitation is determined by their highest level of limitation in any of these activities. For example, if a person has a profound limitation with a communication task and a moderate limitation with a self-care task, they person is categorised as having a profound disability.
A person has a schooling restriction if, because of their disability, they:
A person has an employment restriction if, because of their disability, they:
A person with a ‘schooling/employment restriction only' is someone who reported no limitations with any of the core activities but reported having difficulty with schooling and/or employment activities.
Information was collected using the short-form version of the questions used in the ABS’ monthly Labour Force Survey.
Two changes were made to the employment questions for the 2018–19 NATSIHS.
The first change was that all references to the Community Development Employment Projects (CDEP) were replaced with the Community Development Program (CDP). The labour force status of a person on the CDP depends on whether they had another job and other factors.
The other change was that ‘unpaid trainee work’ was added to the list of categories for payment arrangements to align with changes made to the ABS’ standard employment module. Unpaid trainees were previously categorised as ‘Other’. It is expected that the population in this category is small.
The populations affected by these two changes are likely to be insignificant so there is no break in time series for the 2018–19 NATSIHS.
Differences in household types and compositions, and their requirements relative to income, can be taken into account by the application of equivalence scales. These scales are a set of ratios which, when applied to the income of different household or income unit types, produce standardised estimates of income which reflect the households' relative well-being. The modified Organisation for Economic Co-operation and Development (OECD) equivalence scale (1994) was used.
Equivalised income is derived by calculating an equivalence factor and then dividing income by that factor. The equivalence factor is built up by allocating points to each person in the household unit and summing those points. One point is allocated to the first adult in the unit, 0.5 points for each other person aged 15 years and over, and 0.3 points for each person aged less than 15 years. For example:
Equivalised income is available in dollar amounts and deciles.
‘Family composition’ is created through the relationships that exist between a single ‘responsible adult’ and each other member of that family living in the household. Family composition is then allocated on the basis of whether the types of relationships given below are present or not in the family in the following order of precedence.
The definition of family used for the 2018–19 NATSIHS is a more restrictive definition than the ordinary notion of the term ‘family’ which generally includes relatives whether they live together or not. This is a reflection of the fact that, for survey-based research, it is necessary to place some physical bound on the extent of family for the purposes of being able to collect family data.
A health action is an action taken by a person in the two weeks prior to interview or, for admission to hospital, in the 12 months prior to interview, related to their health. When interpreting health action data, the following points should be noted.
Information was collected on broad range of health conditions, with the primary focus being on those that were current and long-term. A current long-term health condition is an illness, injury or disability which was current at the time of the interview and which had lasted at least six months, or which the person expected to last for six months or more.
Information on specific health conditions was collected in individual modules, as well as a general long-term health conditions module. Questions varied to take into account differences between non-remote and remote populations and demographic characteristics. For example, males and females were asked about different types of cancer testing.
Interviewers coded reported conditions using an extensive pick list of conditions built into the computer based questionnaire. For output purposes, conditions are grouped together based on the International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10).
The following should be taken into consideration when using health conditions data.
The 2018–19 NATSIHS uses the short personal income module instead of the basic module used in the 2012–13 NATSIHS.
In 2012–13, the Community Development Employment Projects (CDEP) was included as a category when asking about sources of personal income. As CDEP was discontinued in 2013, these questions were not included in the 2018–19 NATSIHS. Instead, questions were asked about the Community Development Program (CDP).
In the 2018–19 NATSIHS, the deciles for both household and personal income are not taken from the deciles within the survey. Instead, a national figure is used (which includes both non-Indigenous and Aboriginal and Torres Strait Islander households), meaning there will not necessarily be 10% of the in scope population within each decile. The decile boundaries from the 2017–18 NHS have been used, and adjusted for inflation using the Consumer Price Index to account for enumeration period differences between the 2017–18 NHS and the 2018–19 NATSIHS. This is a similar approach to that used in the 2012–13 NATSIHS and 2014–15 NATSISS.
The dollar amount cut-offs for equivalised household income deciles, gross weekly income of household deciles and gross weekly personal income deciles are available in the data item list via the Downloads tab.
Information about medication use was only collected in non-remote areas. Interviewers recorded the Australian Register of Therapeutic Goods Administration (TGA) identification number of each medication taken by the respondent. These were either:
For medications without an AUST R or AUST L code (for example, medications obtained overseas), interviewers were able to record details of the medication which were later coded by office staff. Up to 50 different medications were able to be recorded.
Therapeutic substances reported were coded as either medications or dietary supplements.
The categorisation of substances as either medications or dietary supplements has been adopted for the purposes of describing data collected in the survey and should not be assumed to be an exact description of the contents of either category. For example, while the ATC includes codes for vitamins and minerals and other dietary supplements, such supplements were coded to the FSANZ supplements classification.
For the purpose of this survey, dietary supplements included:
The collection method for this topic varied between non-remote and remote areas.
Substance use is likely to be under-reported.
COMPARABILITY WITH PREVIOUS SURVEYS
The ABS previously conducted the NATSIHS in 2012–13 and 2004–05. In addition, the National Health Survey (NHS) conducted in 2001 included an Aboriginal and Torres Strait Islander sample known as the NHS (I).
The 2018–19 and 2012–13 surveys largely employed the same methodology and survey content to allow for comparability over time. Information about differences between the various iterations of the survey can be found below.
Between 2011 and 2016, the Aboriginal and Torres Strait Islander population increased by 18.4% or 100,800 people. When comparing estimates from the 2018–19 NATSIHS with previous surveys of the Aboriginal and Torres Strait Islander population, users should be aware of the large increase in the Aboriginal and Torres Strait Islander population and consider the impact this may have when interpreting change over time.
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