Changing Patterns of Mortality in Australia methodology

For information on the institutional environment of the Australian Bureau of Statistics (ABS), including the legislative obligations of the ABS, financing and governance arrangements, and mechanisms for scrutiny of ABS operations, please see ABS Institutional Environment.

Statistics presented in Changing Patterns of Mortality in Australia, 1968-2017 (cat. no. 3303.0.55.003) are drawn from the ABS Causes of Death collection, which is sourced from death registrations administered by the various state and territory Registry of Births, Deaths and Marriages. It is a legal requirement of each state and territory that all deaths are registered. Information about the deceased is supplied by a relative or other person acquainted with the deceased, or by an official of the institution where the death occurred on a Death Registration Form. As part of the registration process, information on the cause of death is either supplied by the medical practitioner certifying the death on a Medical Certificate of Cause of Death, or supplied as a result of a coronial investigation.

Death records are provided electronically to the ABS by individual Registrars on a monthly basis. Each death record contains both demographic data and medical information from the Medical Certificate of Cause of Death, where available. Information from coronial investigations is provided to the ABS through the National Coronial Information System (NCIS).

Statistics presented in Changing Patterns of Mortality in Australia, 1968-2017 (cat. no. 3303.0) are drawn from the ABS Causes of Death collection which includes all deaths that occurred and were registered in Australia, including deaths of persons whose usual residence was overseas. Deaths of Australian residents that occurred outside Australia may be registered by individual Registrars, but are not included in ABS deaths or causes of death statistics.

From the 2007 reference year, the scope of the collection is:

• all deaths registered in Australia for the reference year and received by the ABS by the end of the March quarter of the subsequent year; and
• deaths registered prior to the reference year but not previously received from the Registrar nor included in any statistics reported for an earlier period.
   

For example, records received by the ABS during the March quarter of 2018 which were initially registered in 2017 or prior (but not forwarded to the ABS until 2018) are assigned to the 2017 reference year. Any death registrations relating to the 2017 reference period which are received by the ABS after the end of the March 2018 quarter are assigned to the 2018 reference year.

For collection scope prior to 2007, see Explanatory notes in Causes of Death Australia, 2006, and earlier publications.

Data in the Causes of Death collection include causes of death information, as well as some demographic items. Causes of death information is obtained from the Medical Certificate of Cause of Death (for general deaths), the Medical Certificate of Cause of Perinatal Death (for perinatal deaths) and the National Coronial Information System (for coroner-certified deaths). Causes of death are coded according to the International Classification of Diseases (ICD).

Issues for causes of death data:

• The primary objective of the owner of the source data can differ from the information needs of the statistical users. Registrars of Births, Deaths and Marriages and coroners have legislative and administrative obligations to meet, as well as being the source of statistics. As a result, the population covered by the source data, the time reference period for some data, and the data items available in the registration system, may not align exactly with the requirements of users of the statistics.
• There can be differences between the defined scope of the population (i.e. every death occurring in Australia) and the actual coverage achieved by the registration system. Levels of registration can be influenced by external factors and coverage achieved will be influenced by the steps taken by the owners of death registration systems to ensure all deaths are registered. For example, a death certificate may need to be produced in order to finalise certain other legal requirements e.g. finalisation of a person's estate.
• There are eight different registration systems within Australia. Each jurisdiction's registration system, while similar in many ways, also has a number of differences. These can include the types of data items collected, the definition of those collected data items, and business processes undertaken within Registries of Births, Deaths and Marriages including coding and quality assurance practices.
   

The ABS Causes of Death dataset, which provides the statistics for Changing Patterns of Mortality in Australia, 1968-2017 , is released annually, approximately nine months after the end of the reference period and in conjunction with Deaths, Australia (cat. no. 3302.0). The Causes of Death publication, released on 26 September 2018, contains the 2017 data which completes the fifty-year time-series of mortality data used in this publication.

Prior to the release of the 2015 dataset, causes of death data had been released approximately 15 months after the end of the reference period, however changes to process allowed for more timely access to Australian mortality data. For more information see A more timely annual collection: changes to ABS processes (Technical Note) in Causes of Death, Australia, 2015 (cat. no. 3303.0).

There is a focus on fitness for purpose when causes of death statistics are released. To meet user requirements for accurate causes of death data it is necessary to obtain information from other administrative sources before all information for the reference period is available. This specifically applies to coroner-certified deaths, where extra information relating to the death is provided through police, toxicology, autopsy and coronial finding reports. A balance therefore needs to be maintained between accuracy (completeness) of data and timeliness. ABS provides the data in a timely manner, ensuring that all coding possible can be undertaken with accuracy prior to publication.

As coroner-certified deaths can have ill-defined causes of death until a case is closed within the coronial system, a revisions process was introduced to enhance the cause of death output for open coroner cases. This process enables the use of additional information for coding relating to coroner-certified deaths at approximately 12 and/or 24 months after initial processing. See Explanatory Notes 57-60 in Causes of Death, Australia, 2017 (cat. no. 3303.0) and the Causes of Death Revisions, 2013 Final Data Technical Note in Causes of Death, Australia, 2015 (cat. no. 3303.0), for further information on the revision process.

Changing Patterns of Mortality in Australia, 1968-2017, includes preliminary data for 2017 and 2016, revised data for 2015 and final data for 2014 back to 2006. No revisions were applied to data prior to 2006.

Issues for causes of death data:

• A balance is maintained between accuracy (completeness) and timeliness, taking into account the different needs of users and maximising the fitness for purpose of the data. Documentation including explanatory notes and technical notes are provided for causes of death statistics, and can be found in the Causes of Death, Australia publication (cat. no. 3303.0). These should be used to assess the fitness for purpose of the data to ensure informed decisions can be made.
• The timeliness of administrative information that supports cause of death coding can be impacted by legislative requirements, systems and resources available to maintain/update systems.
   

Non-sampling errors may influence accuracy in datasets which constitute a complete census of the population, such as the Causes of Death collection. Non-sampling error arises from inaccuracies in collecting, recording and processing the data. Every effort is made to minimise non-sampling error by working closely with data providers, undertaking quality checks throughout the data processing cycle, training of processing staff, and efficient data processing procedures.

The ABS has implemented a revisions process that applies to all coroner-certified deaths registered after 1 January 2006. This is a change from preceding years where all ABS processing of causes of death data for a particular reference period was finalised approximately 13 months after the end of the reference period. The revisions process enables the use of additional information relating to coroner-certified deaths as it becomes available over time, resulting in increased specificity of the assigned ICD-10 codes. See Explanatory Notes 57-60 in Causes of Death, Australia, 2017 (cat. no. 3303.0) and the Causes of Death Revisions, 2014 Final Data Technical Note in Causes of Death, Australia, 2016 (cat. no. 3303.0), for further information on the revision process.

Issues for causes of death data:

• Completeness of the dataset e.g. impact of registration lags, processing lags and duplicate records.
• Extent of coverage of the population (while all deaths are legally required to be registered some cases may not be registered for an extended time).
• Some lack of consistency in the application of questions or forms used by administrative data providers.
• The level of specificity and completeness in coronial reports or doctor's findings on the Medical Certificate of Cause of Death.
• Errors in the coding of the causes of a death to ICD-10. The majority of cause of death coding is undertaken through an automated coding process, which is estimated to have a very high level of accuracy. Human coding can be subject to error, however the ABS mitigates this risk through rigorous coder training, detailed documentation and instructions for coding complex or difficult cases, and extensive data quality checks.
• Cases where coronial proceedings remain open at the end of ABS processing for a reference period are potentially assigned a less specific ICD-10 cause of death code.
• Where coroner-certified deaths become closed during the revisions process, additional information is often made available, making more specific coding possible.
   

Use of explanatory notes and technical notes released with the statistics is important for assessing coherence within the dataset and when comparing the statistics with data from other sources. Changing business rules over time and/or across data sources can affect consistency and hence interpretability of statistical output, especially when assessing time series data. As Changing Patterns of Mortality in Australia, 1968-2017 is drawn from the ABS Causes of Death collection, users have been referred to explanatory and technical notes published in Causes of Death, Australia (cat. no. 3303.0) where further explanation is needed.

The ICD is the international standard classification for epidemiological purposes and is designed to promote international comparability in the collection, processing, classification, and presentation of cause of death statistics. The classification is used to classify diseases, conditions, injuries and external events as recorded on many types of medical records as well as death records. It is used for both morbidity and mortality purposes, with the morbidity version incorporating clinical modifications. The ICD is revised periodically to incorporate changes in the medical field. The 10th revision of ICD (ICD-10) was used for coding the 1998-2017 data, ICD-9 for 1979-1997, and ICD-8 for 1968-1978 presented in this publication.

Issues for causes of death data:

• Changes to questions, scope etc. over time can affect the consistency of data collected over the period, even when the source of the data is the same. These changes can be the result of legislative or program objective changes.
• The completeness or quality of older versus newer data can also impact on comparisons across time or domains.
• Statistical concepts for questions are not always suited to the administrative purpose or the means of collection.
   

In 2014, the ABS implemented Iris, a new automated coding software product for assisting in the processing of cause of death data. This software has been used from 2013 reference year cause of death data onwards. With the introduction of new coding software, the ABS also implemented the most up to date versions of the ICD-10 when coding 2013 and 2014-2017 data (using the 2013 and 2015 versions, respectively), and improved a number of coding practices to realign with international best practice. As part of this, the ABS began a review of its method of coding perinatal deaths which, for the 2013-2017 data published in this issue, has meant a change to the method used for assigning an underlying cause of death to neonatal deaths. It is advised that data users refer to the below technical notes for further details.

• Technical Note 1, Changes to Perinatal Death Coding, in Causes of Death, Australia, 2014 (cat. no. 3303.0); and
• Technical Note 1, ABS Implementation of the Iris Software: Understanding Coding and Process Improvements, in Causes of Death, Australia, 2013 (cat. no. 3303.0).

The Causes of Death publication contains detailed Explanatory Notes, Technical Notes, Appendices and a Glossary that provide information on the data sources, terminology, classifications and other technical aspects associated with these statistics.

Issues for causes of death data:

• Information on some aspects of statistical quality may be hard to obtain as information on the source data has not been kept over time. This is related to the administrative rather than statistical purpose of the collection of the source data.
   

The Causes of Death, Australia (cat. no. 3303.0) publication includes information, articles, and a series of data cubes providing detailed data on specific causes of death. This data has been analysed in Changing Patterns of Mortality in Australia, 1968-2017. The ABS observes strict confidentiality protocols as required by the Census and Statistics Act (1905). This may restrict access to data at a very detailed level which is sought by some users.

Issues for causes of death data:

• Often an administrative source can provide the basis for statistical information which has a different nature and focus to the source's principal administrative purpose. There may be a reduced focus or availability of funding within the program to ensure the accessibility of information for non-administrative uses.
• Each jurisdiction has its own legislation governing death registration as well as that governing the coronial process. Jurisdictions also have privacy legislation which governs the accessibility of the statistics.
• The ABS observes strict confidentiality protocols as required by the Census and Statistics Act (1905). This may restrict access to data at a very detailed level which is sought by some users.
• A national causes of death unit record file can be obtained through the Australian Coordinating Registry (which is housed at the Queensland Registry of Births, Deaths and Marriages) by sending an email to BDM.CODURF@justice.qld.gov.au (data available on application for legitimate research purposes only).

If the information you require is not available from the publication or the data cubes, then the ABS may also have other relevant data available on request. Inquiries should be made to the National Information and Referral Service on 1300 135 070 or by sending an email to client.services@abs.gov.au.

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