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Life tables

Introduction

A life table is a statistical model used to represent mortality of a population. 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 tables in this spreadsheet 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 for the Australian and state and territory life tables are based on death registrations and estimated resident population for the period 2007–2009.

A life table may be complete or abridged, depending on the age interval used in the compilation. Life tables in this spreadsheet are complete life tables—they contain data by single years of age. Abridged life tables contain data for five-year age groups.Life tables are presented separately for males and females.

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 in size.

To construct a life table, data on population, deaths and births are needed. Mortality rates are smoothed to avoid fluctuations in the data. Apart from mortality rates themselves (qx), all other functions of the life table are derived from qx. The life tables presented in this publication 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.

The 2007–2009 life tables differ from those published prior to the 1995 edition of Deaths, Australia (cat.no.3302.0) in a number of respects. Firstly, they are based on three years of death registrations and estimated resident population data. This is designed to reduce the effect of year-to-year statistical variations, particularly at younger ages where there are small numbers of deaths, and at very old ages where the population at risk is small. Secondly, the deaths and population data are based on Australian residents who are physically present in Australia over the three-year period; i.e. Australian residents temporarily overseas are excluded. Thirdly, they have been actuarially graduated on the same principles which are used for the quinquennial Australian life tables prepared by the Australian Government Actuary.

Life tables for the states and territories are produced on the same principles as the Australian life tables. For the periods 1994–1996 to 1999–2001 these are available in the Demography (cat.nos. 3311.1–3311.8) set of publications. State and territory life tables for the period 2000–2002 are available on request. State and territory life tables for 2001–2003 onwards are published in Life Tables (cat.nos. 3302.1.55.001–3302.8.55.001). State and territory life tables for 2007–2009 are scheduled for release on 8 December 2010.

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. Mortality rates derived from these life tables are used as inputs to ABS population projections. For further information see Population Projections, Australia (cat.no. 3222.0).