Aboriginal and Torres Strait Islander Status in Death Registrations

Recording and Reporting of Aboriginal and Torres Strait Islander Deaths
It was previously believed that most deaths of Aboriginal and Torres Strait Islander Australians were registered with the relevant state or territory Registrar of Births, Deaths and Marriages as required by legislation. However, over many years the ABS has been aware that not all of these deaths are reported and recorded as Aboriginal and Torres Strait Islander Australians in the death registration information provided to the Registrars. Consequently, to varying degrees across and within jurisdictions, and over time, mortality rates based solely on death registration information for Aboriginal and Torres Strait Islander Australians have been understated.

More recently, the ABS has become aware that some deaths of Aboriginal and Torres Strait Islander people are registered much later than other deaths. Further, in some cases, some known deaths are still to be registered as the relevant forms and information have not yet been provided to the relevant Registrar for inclusion in the jurisdiction’s death register.

The non-registration and late registration of deaths represent significant impediments to compiling and reporting accurate mortality statistics for Aboriginal and Torres Strait Islander Australians. While recent improvements in death registration compliance and completeness are welcome, changes over time also present challenges for meaningful analysis of the underlying trends associated with closing the gap between life expectancy at birth and mortality rates experienced by Aboriginal and Torres Strait Islander peoples and other Australians.

Assessing Under-Identification
Over the last two decades, the ABS has applied various methodological techniques to estimate the extent of under identification in death registrations. For the 1991-1996 intercensal period, the ABS used the Preston-Hill method to adjust the number of deaths in the compilation of life tables and life expectancy estimates for Aboriginal and Torres Strait Islander Australians. For the 1996-2001 intercensal period, the ABS used the Bhat method. A summary of these methods is described in Discussion Paper: Assessment of Methods for Developing Life Tables for Aboriginal and Torres Strait Islander Australians, 2006 (cat. no. 3302.0.55.002)

To give an indication of Indigenous identification rates in subsequent death registrations, ABS compiled and released implied coverage rates annually in Deaths, Australia (cat. no. 3302.0). These implied coverage rates compared the number of death registrations recorded as Aboriginal and Torres Strait Islander people with an “expected” number of deaths. These expected deaths were derived by applying age-sex specific death rates from previously compiled life tables to estimates and projections of the Aboriginal and Torres Strait Islander population for the reference year. This methodology was somewhat circular, and substantially reliant on:

• the derivations and assumptions made in compiling the life tables and population estimates continuing to apply through time to subsequent periods, and
• the assumption that mortality rates had not changed from year to year.

Consequently, for some jurisdictions, the implied coverage rates were greater than 100 (that is, there were more observed death registrations than expected). For other jurisdictions, the implied coverage rates were well below 100 implying a substantial under identification of Aboriginal and Torres Strait Islander deaths in death registrations. No account was made for late or under registration in these calculations.

Data Linkage
From 2007, the ABS has introduced two improvements to increase Aboriginal and Torres Strait Islander identification rates. The first was to make use of Indigenous status from Medical Certificate of Cause of Death records where available electronically. This had very little impact on the number of Aboriginal and Torres Strait Islander death registrations. For further information, see Explanatory Note 36 in Deaths, Australia, 2007 (cat. no. 3302.0).

The second improvement was a data linking study. The 2006 ABS Census Data Enhancement Indigenous Mortality Study provided a new basis for estimating the completeness of Indigenous status in death registrations. Death registration records for deaths which occurred after the 2006 Census were linked to 2006 Census records. Identification rates were calculated and used in compiling a new set of life tables and estimates of life expectancy at birth for Aboriginal and Torres Strait Islander Australians. For more information, see Information Paper: Census Data Enhancement - Indigenous Mortality Quality Study, 2006-07 (cat. no. 4723.0), Discussion Paper: Assessment of Methods for Developing Life Tables for Aboriginal and Torres Strait Islander Australians, 2006 (cat. no. 3302.0.55.002) and Experimental Life Tables for Aboriginal and Torres Strait Islander Australians, 2005—2007 (cat. no. 3302.0.55.003).

The ABS is aware of other public health research projects linking death registration records to health records and the comparison of Indigenous status from each source. These provide an additional perspective on the differences between Indigenous status identification in death registration records and these other data sources. However, without a linkage to the basis for population estimates (i.e. Census records), there is the potential for inconsistency between the Indigenous status of deaths and the Indigenous status of the population. This will lead to what is termed numerator/denominator bias in mortality rates.

Planned work program
For the 2011 Census, the ABS will be repeating the linkage of death registrations that occurred after the Census to 2011 Census records. The results of this linkage project will be utilised to compile new Indigenous identification rates to adjust the number of deaths for 2010 to 2012 calendar years when compiling a set of life tables and life expectancy at birth estimates for Aboriginal and Torres Strait Islander Australians. Wherever possible for the 2011 Census cycle, methodologies consistent with the 2006 Census cycle will be adopted to ensure comparability between the life expectancy at birth estimates for 2005-2007 and 2010-2012. This will enable a valid comparison of estimates to determine whether there has been a change in the gap between life expectancy at birth estimates between Aboriginal and Torres Strait Islander peoples and other Australians between 2005-2007 and 2010-2012. These results will be reported in accompanying technical material with the release of Life Tables for Aboriginal and Torres Strait Islander Australians, 2010—2012 (cat. no. 3302.0.55.003) in late 2013.

ABS continues to work in collaboration with state and territory Registrars of Births, Deaths and Marriages to implement or enhance quality checks at appropriate stages of processing to improve the quality of death registration data, both within the Registries and the ABS. The quality of Aboriginal and Torres Strait Islander death registrations is a particular focus of this collaboration.