Life expectancy methodology

Internationally, life tables are used to measure mortality. In its simplest form, a life table is generated from age-specific death rates and the resulting values are used to measure mortality, survivorship and life expectancy. The life table depicts the mortality experience of a hypothetical group of newborn babies throughout their entire lifetime. It is based on the assumption that this group is subject to the age-specific mortality rates of the reference period. Typically this hypothetical group is 100,000 persons in size.

Life tables in this release are current, or period, life tables, based on death rates for a short period of time during which mortality has remained much the same. Mortality rates used in the Australian and state and territory life tables are based on the occurrence of deaths in the 2021-2023 period and the estimated resident population at the mid-point of that period. The life tables do not take into account future assumed improvements in mortality.

Life tables may be complete or abridged, depending on the age interval used in the compilation. Life tables in these spreadsheets are complete life tables—they contain data by single years of age. Abridged life tables contain data for five-year age groups.

Life tables for males and females are released for Australia and states/territories. However, only the life expectancy at birth estimates for males, females and persons are released for Statistical Areas level 4 (SA4).

To construct a life table, data on population, deaths and births is needed. Mortality rates are smoothed to avoid fluctuations in the data. The mortality rate (qx), is the main function of the life table, all other functions are derived from it. The life tables presented in this release contain four columns of interrelated information. These functions are:

• lx - the number of persons surviving to exact age x
• qx - the proportion of persons dying between exact age x and exact age x+1. It is the mortality rate, from which other functions of the life table are derived
• Lx - the number of person years lived within the age interval x to x+1, and
• ex - life expectancy at exact age x

Life tables based on assumed improvements in mortality are produced by the ABS using assumptions on future life expectancy at birth, based on recent trends in life expectancy. These are not the ABS' official life tables and are only used as inputs to ABS population projections. For further information see Population Projections, Australia.

The 2021-2023 national and state/territory life tables have been compiled using the final rebased ERP based on the 2021 Census of Population and Housing data.

With the release of the 2010-2012 life tables, a small refinement was made to the method to bring Australia's mortality rates (qx values) into line with other comparable countries. The impact of these changes in life expectancy at birth estimates is minimal, though caution should be applied when interpreting changes to life tables over time. For more information, see:

• Life expectancy
• Technical Note: The Impact of the Revision to Estimated Resident Population on Life Expectancy Estimates
   

Life tables for the states and territories are produced on the same principles as the Australian life tables with the exception of the crude death rate, m(x). Crude death rates are smoothed using the Australian life table through the application of the Hodrick-Prescott filter (Hodrick and Prescott, 1977). This overcomes problems associated with excessive noise in the single year of age rates. In addition, some minor smoothing and suppression of outliers is often required to achieve reasonable mortality curves with satisfactory goodness-of-fit statistics.

State and territory life tables produced by the ABS are available for:

• 1994-1996 to 1999-2001: published in Deaths, Australia
• 2000-2002: available on request
• 2001-2003 to 2019-2021: published in Life tables
• 2020-2022 onwards: published in Life expectancy

Life expectancy at birth estimates for Statistical Areas Level 4 are released for males, females and persons. They have been calculated with reference to state and territory life tables, using the Brass' Logit System (Brass, 1975). These small area life tables are based on age-specific death rates for each area, some of which may be zero where no deaths are recorded at these ages. The Brass' Logit technique enables the calculation of smooth abridged life tables for regions which have deficient age-specific death rates, by adjusting them with reference to a standard life table. The technique does not alter the overall level of mortality, but the age-specific functions of the life table are smoothed.

The Brass' Logit technique essentially compares mortality between the regional and standard life tables across ages, then a line of best fit is calculated to describe that relationship by age. The line of best fit is then used in conjunction with the standard life table to determine death rates for the small area life table. For a more detailed description of the Brass' Logit System, see Methods for Estimating Fertility and Mortality from Limited and Defective data (Brass, 1975).

Life expectancy estimates for the Aboriginal and Torres Strait Islander population was published on 29 November 2023 in Aboriginal and Torres Strait Islander life expectancy, 2020-2022.

Estimates of life expectancy at birth for the total population (this release) are derived differently to estimates presented in Aboriginal and Torres Strait Islander life expectancy, 2020-2022. Estimates of life expectancy at birth for the Aboriginal and Torres Strait Islander population are derived from abridged life tables with an upper age limit of 85 years and over, using numbers of deaths registered in 2020-2022 and the population as at 30 June 2021. Estimates of life expectancy for the total population are based on complete life tables with an upper age group of 120 years and over, using deaths according to month of occurrence in 2020-2022 and quarterly population estimates. In addition, smoothing processes applied to both sets of life tables differ.

Other ABS products which may be of interest to users include:

• Historical Population
• Australian Statistical Geography Standard (ASGS) Edition 3
• Births, Australia
• Deaths, Australia
• Causes of Death, Australia
• Aboriginal and Torres Strait Islander life expectancy
• Population Projections, Australia
• National, state and territory population
   

ABS products and releases are available free of charge from the ABS website http://www.abs.gov.au. Click on Statistics to gain access to the full range of ABS statistical and reference information.

Detailed life expectancy statistics are available electronically from the Data downloads section of this release.

• Life tables, age and sex by state and territory of usual residence, 2021-2023
• Life expectancy at birth, sex by Statistical Areas Level 4, 2016-2018 to 2021-2023

The ABS' releases draw extensively on information provided freely by individuals, businesses, governments and other organisations. The efforts of each state and territory's Registries of Births, Deaths and Marriages to improve the data quality, coverage and timeliness of death registration information, processes and systems are noted and valued by the ABS. Their continued cooperation is very much appreciated. Information received by the ABS is treated in strict confidence as required by the Census and Statistics Act 1905.