Provisional Mortality Statistics methodology

The scope of the statistics includes:

• Deaths that occurred and were registered in Australia, including deaths of persons whose usual residence is overseas;
• Deaths occurring within Australian Territorial waters;
• Deaths occurring in Australian Antarctic Territories or other external territories (including Norfolk Island);
• Deaths occurring in transit (i.e. on ships or planes) if registered in the State of 'next port of call'; and
• Deaths of Australian Nationals overseas who were employed at Australian legations and consular offices (i.e. deaths of Australian diplomats while overseas) where able to be identified.
   

The scope of the statistics excludes:

• Deaths of Australian residents that occurred outside Australia but have been registered by individual Registrars;
• Repatriation of human remains where the death occurred overseas;
• Deaths of foreign diplomatic staff in Australia (where these are able to be identified); and
• Stillbirths (fetal deaths).
   

This report contains statistics compiled using different methods to those used when compiling annual data on deaths and causes of death. Key differences include:

1. This report focusses only on doctor certified deaths. Annual reports cover all deaths including those that are doctor certified and those that were referred to a coroner.
2. Data in this report are based on the date of occurrence of the death. Annual reports generally present data based on date of registration.
3. Data in this report are based on the state or territory of registration. Data in annual reports are based on the state or territory of usual residence of the deceased.
4. Data in this report are considered to be provisional. Data released in annual reports are considered to be final (with the exception of revisions for coroner referred deaths).
    

Data for the current reference period and data used to derive baseline counts (maximum, minimum and average) are based on these methods enabling strong comparison over time.

For more information regarding the scope of the annual Deaths, Australia and Causes of Death, Australia publications see Explanatory notes on the Methodology page in catalogue numbers 3302.0 and 3303.0 on the ABS website.

When a death occurs, the cause of that death is either certified by a doctor using a Medical Certificate of Cause of Death (MCCD), or the death is referred to a coroner for further investigation. Data in this report cover only those deaths that are certified by a doctor. In Australia approximately 86-89% of deaths are certified by a doctor.

Almost all external causes of death (e,g. suicides, accidents and assaults) are referred to a coroner and are therefore not covered in this report.

Although there is variation across jurisdictions in what constitutes a death that is reportable to a coroner, they are generally reported in circumstances such as:

• where the person died unexpectedly and the cause of death is unknown
• where the person died in a violent or unnatural manner
• where the person died during, or as a result of an anaesthetic
• where the person was 'held in care' or in custody immediately before they died
• where the identity of the person who has died is unknown.
   

Counts of deaths in this report will not be comparable with those reported in the annual Deaths, Australia or Causes of Death, Australia publications which include both doctor and coroner certified deaths.

There are two dates that are recorded on a death registration for all deaths that occur in Australia - the date on which the death occurred and the date on which the death was registered. Data in this report are compiled on date of occurrence.

Date of occurrence and date of registration will differ for all deaths, and the length of time by which they differ can vary considerably. Deaths are not reported to the ABS until they are registered, so the length of time between death and registration affects:

• The timeliness of information reported; and
• The ability to measure true change in mortality over time.
   

The average time lag between death and registration can vary, although in general deaths certified by a doctor are registered sooner. Coroner certified deaths undergo extensive investigative processes which can delay registration times.

As lag times between death and registration are longer for coroner referred deaths, these are excluded from these reports.

Data in this release are compiled by state or territory in which the death was registered. In the majority of cases, the death is registered in the state in which it occurred. Data in the annual Deaths, Australia and Causes of Death, Australia reports are compiled by the state or territory of usual residence of the deceased, regardless of where in Australia the death occurred and was registered.

Deaths of persons usually resident overseas which occur in Australia are included in the state/territory in which their death was registered. They are also included in counts of deaths based on usual residence of the deceased.

Statistics in this release are provisional and will be subject to additional processes prior to being released as part of the annual Deaths and Causes of Death datasets. Changes that may occur are:

• The number of deaths may change.
• Demographic variables may change.
• The causes of death may change.
   

Counts of deaths in the annual Deaths, Australia (cat. no. 3302.0) and Causes of Death, Australia (cat. no. 3303.0) are considered final. Causes of death for coroner referred deaths are subject to a revisions process. Further information on this revisions process can be found in the Explanatory notes in the Methodology for Causes of Death, Australia (cat. no. 3303.0).

As registrations for deaths that occurred in previous reference periods are sent to the ABS, these will be counted in their date of occurrence and therefore each release will represent a more complete count of the number of deaths that occurred in that reference period.

Data can be impacted by changes in practices within one or more of the Registries of Births, Deaths and Marriages and therefore caution should be exercised when assessing week to week movements.

Mortality data for 2020 are compared to an average baseline. The baseline is an arithmetic average of the previous 5 years of deaths from 2015 to 2019 based on year and week of occurrence. Minimum and maximum counts from 2015-19 are also included to provide an indication of the range of previous counts.

Baselines are compiled based on weekly counts of deaths from all causes and for specified causes of death. Weekly baseline information strengthens comparability by accounting for seasonal patterns of mortality. While baselines provide a point for comparison they do not provide an indication of the statistical significance of any deviation from that baseline.

The International Classification of Diseases (ICD) is the international standard classification for epidemiological purposes and is designed to promote international comparability in the collection, processing, classification, and presentation of causes of death statistics. The classification is used to classify diseases and causes of disease or injury as recorded on many types of medical records as well as death records.

The ICD is revised periodically to incorporate changes in the medical field. Currently the ICD 10th revision is used for Australian causes of death statistics.

The ICD-10 is a variable-axis classification meaning that the classification does not group diseases only based on anatomical sites, but also on the type of disease. Epidemiological data and statistical data are grouped according to:

• epidemic diseases;
• constitutional or general diseases;
• local diseases arranged by site;
• developmental diseases; and
• injuries.
   

For example, a systemic disease such as sepsis is grouped with infectious diseases; a disease primarily affecting one body system, such as a myocardial infarction, is grouped with circulatory diseases; and a congenital condition, such as spina bifida, is grouped with congenital conditions.

For further information about the ICD refer to WHO International Classification of Diseases (ICD).

The versions of the ICD 10th Revision are available online.

The Update and Revision Committee (URC), a WHO advisory group on updates to ICD-10, maintains the cumulative and annual lists of approved updates to the ICD-10 classification. The updates to ICD-10 are of numerous types including the addition and deletion of codes, changes to coding instructions and modification and clarification of terms.

From the 2013 reference year, the ABS implemented a new automated coding system called Iris.

The 2013-2020 data coded in the Iris system applied updated versions of the ICD-10 when coding multiple causes of death, and when selecting the underlying cause of death. The 2020 reference year causes of death data presented in this publication was coded using version 5.8.0 of Iris software. Version 5.8.0 applied the WHO ICD-10 updates (2020 version) which have resulted in minor changes to output. More information on Iris and ICD-10 versioning can be found in the table below.  For details of further impacts of this change from 2013 data onwards, please see the ABS Implementation of the Iris Software: Understanding Coding and Process Improvements Technical Note, in the Causes of Death, Australia, 2013 publication. 

The cumulative list of ICD-10 updates can be found online.

In response to the COVID-19 pandemic, the WHO issued the ICD emergency codes U07.1 COVID-19, virus identified and U07.2 COVID-19 virus not identified. These codes are used when assigning causes to confirmed or suspected COVID-19 deaths.

Due to the public health importance of COVID-19, the WHO directed that the new coronavirus strain be recorded as the underlying cause of death, i.e. the disease or condition that initiated the train of morbid events, when it is recorded as having caused death.

Deaths due to COVID-19 are included in the total for all deaths certified by a doctor. They are not included in deaths due to respiratory diseases or any of the other specified causes included in this report.

The number of weekly COVID-19 infections (not deaths) shown in Graph 1 of this report reflects the number of newly confirmed COVID-19 cases reported and updated daily by the Australian Department of Health. Information on newly identified COVID-19 infections is sourced from State and Territory Departments of Health and collated into a national figure by the Department of Health. Data was extracted by the ABS on 01 January 2021.

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.

Data cells with small values have been randomly assigned to protect confidentiality. As a result some totals will not equal the sum of their components. Cells with 0 values have not been affected by confidentialisation.

Age-standardised death rates enable the comparison of death rates over time and between populations of different age-structures. The ABS uses the direct method of age-standardisation as it allows for valid comparisons of mortality rates between different study populations and across time. This method was agreed to by the ABS, Australian Institute of Health and Welfare (AIHW) and other stakeholders. For further information see: AIHW (2011) Principles on the use of direct age-standardisation in administrative data collections: for measuring the gap between Indigenous and non-Indigenous Australians. Cat. no. CSI 12. Canberra: AIHW.

The direct method has been used throughout the publication and data cubes for age-standardised death rates. Age-standardised death rates for specific causes of death with fewer than a total of 20 deaths have not been published due to issues of robustness. For further information, see Appendix: Principles on the use of direct age-standardisation, from Deaths, Australia, 2010.

Age-standardised death rates (SDRs) in this publication have been calculated using quarterly population estimates and short-term population projections. SDRs for baseline years (2015-2019) have been calculated using quarterly estimated resident population (ERP) published in 'National, state and territory population, September 2020' released on 18 March, 2021. See 'Revision status' in the Methodology section of that release for details of the status of quarterly population data used for calculating baseline rates. The quarterly estimates used for calculating weekly rates for the relevant year are as follows: weeks 1-13  (March Qtr ERP); weeks 14-26 (June Qtr ERP); weeks 27-39 (Sept. Qtr ERP) and; weeks 40-53 (Dec. Qtr ERP).

Age-standardised death rates for 2020 and 2021 are based on population estimates (published in 'National, state and territory population') or short-term population projections. Since the most recently released population estimates lag the provisional mortality data by several months, short-term population projections have been used for calculating rates for some weeks. The population projections are based on the most recently available population estimate plus projected components of population growth. Projected births, deaths and interstate migration are based on previously observed data published in 'National, state and territory population'. Projected overseas migration is based on the latest overseas arrivals and departures data, as well as previously observed overseas migration published in 'National, state and territory population'. See the relevant footnotes in the data cubes of this publication for specific details of the ERP/projections used for the calculation of SDRs for weeks in 2020 and 2021.

Mortality rates derived from administrative data counts may be subject to natural random variation, especially for small counts. Confidence intervals (CIs) for an SDR can help quantify this variability. CIs included in this publication indicate a 95% probability that the 'true' SDR is contained within the lower and upper limits of the CI. CIs have been calculated using the standard method and formulae can be sourced from Breslow and Day (1987) in the 'Statistical methods in cancer research' publication. Further information on the calculation of CIs can also be found on the METeOR website (see National Indigenous Reform Agreement: PI 08 - Tobacco smoking during pregnancy, 2016).

The registration of deaths is the responsibility of the eight individual state and territory Registrars of Births, Deaths and Marriages.

In order to complete a death registration, the death must be certified by either a doctor using the Medical Certificate of Cause of Death (MCCD) or by a coroner. This release includes deaths that have been certified by a doctor only.

For doctor certified deaths, information about the cause of death is supplied by the medical practitioner certifying the death via the MCCD (or MCCPD for perinatal deaths). Other information about the deceased is supplied via the Death Registration Form, which is informed by a relative or other person acquainted with the deceased, or by an official of the institution where the death occurred. Registrars require information from both sources to complete a death registration. It should be noted that legislative requirements for registering a death differ across jurisdictions and this can impact on the timeliness of registration and reporting.

The information is provided to the Australian Bureau of Statistics by individual Registrars for processing, coding and compilation into aggregate statistics. Registrars report all deaths that were registered in a given month to the ABS at the start of the following month.

The following diagram shows the process undertaken in producing cause of death statistics for doctor certified deaths in Australia.