Life tables methodology

1 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. For more information, see Demographic Methods and Concepts (Rowland, 2003).

2 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 2016-2018 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.

3 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.

4 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 the Statistical Area level 4 (SA4).

5 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.

6 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, 2017 (base) to 2066 (cat. no. 3222.0).

7 The 2016-2018 national and state/territory life tables have been compiled using the final rebased ERP based on the 2016 Census data.

8 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 tables, States, Territories and Australia, 2011-2013 (cat. no. 3302.0.55.001)
• Technical Note: The Impact of the Revision to Estimated Resident Population on Life Expectancy Estimates
   

9 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.

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

• 1994-1996 to 1999-2001: published in the Demography set of releases (cat. no. 3311.1-3311.8);
• 2000-2002: available on request;
• 2001-2003 to 2008-2010: published in Life Tables (cat. no. 3302.1.55.001-3302.8.55.001);
• 2009-2011 onwards: published in Life Tables, States, Territories and Australia (cat. no. 3302.0.55.001).
   

11 Life expectancy at birth estimates for Statistical Area Level 4s 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.

12 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).

13 Life tables for the Aboriginal and Torres Strait Islander population were published in November 2018 in Life Tables for Aboriginal and Torres Strait Islander Australians, 2015-2017 (cat. no. 3302.0.55.003).

14 Estimates of life expectancy at birth for the total population released in Life Tables, States, Territories and Australia, 2016-2018 (cat. no. 3302.0.55.001) are constructed differently to estimates presented in Life Tables for Aboriginal and Torres Strait Islander Australians, 2015-2017 (cat. no. 3302.0.55.003). 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 2015-2017 and the population as at 30 June 2016. 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 2015-2017 and quarterly population estimates. In addition, smoothing processes applied to both sets of life tables differ.

15 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.

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

• Australian Historical Population Statistics (cat. no. 3105.0.65.001)
• Australian Statistical Geography Standard (ASGS): Volume 1 - Main Structure and Greater Capital City Statistical Areas (cat. no. 1270.0.55.001)
• Births, Australia (cat. no. 3301.0)
• Deaths, Australia (cat. no. 3302.0)
• Discussion Paper: Assessment of Methods for Developing Life Tables for Aboriginal and Torres Strait Islander Australians (cat. no. 3302.0.55.002)
• Estimates and Projections, Aboriginal and Torres Strait Islander Australians (cat. no. 3238.0)
• Estimates of Aboriginal and Torres Strait Islander Australians (cat. no. 3238.0.55.001)
• Life Tables (cat. no. 3302.0.55.001)
• Life Tables for Aboriginal and Torres Strait Islander Australians (cat. no. 3302.0.55.003)
• Population Projections, Australia (cat. no. 3222.0)
   

17 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.

18 More detailed life table information can be obtained from data cubes (in Microsoft Excel format) available electronically, from the Data downloads section of this release.

Data cubes

• Table 1: Life tables, States, Territories and Australia, 2016-2018
• Table 2: Life tables, Statistical Area Level 4, 2010-2012 to 2016-2018
   

Australian Historical Population Statistics (cat. no. 3105.0.65.001)

• Life expectancy
   

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Australian Bureau of Statistics, Australian Statistical Geography Standard (ASGS): Volume 1 - Main Structure and Greater Capital City Statistical Areas, cat. no. 1270.0.55.001, ABS, Canberra.

Brass, W 1975, Methods for Estimating Fertility and Mortality from Limited and Defective Data, University of North Carolina at Chapel Hill, Chapel Hill.

Hodrick, Robert; Prescott, Edward C. (1977), Postwar U.S. Business Cycles : An Empirical Investigation, Journey of Money, Credit, and Banking, 20 (1) : 1-16.

Rowland, D. 2003, Demographic Methods and Concepts, Oxford University Press, New York.