A 1992 report recommended that the Commonwealth Government recognise that 'the changing demographic structure of the population requires reassessment of the value and importance, both socially and economically, of life outside traditional work' 3 . Life expectancy is a measure of current mortality rather than a predictor of future lifespan since age-specific death rates can change over time. Life expectancy at birth is often wrongly interpreted to mean that most people die at that age. The average life expectancy gives no indication of the variation in life expectancies. Life expectancy is the average number of additional years a person of a given age and sex might expect to live if they experience the current age-specific death rates from that age onwards through the rest of their life.
Life expectancy is calculated separately for each sex.
This is done one year at a time by taking a hypothetical group of new-born babies and, using the current probability of dying at each year of age, calculating the expected number of survivors at each age. The expected number of survivors slowly diminishes until the whole group have 'died'. Life expectancy at an age is calculated by dividing the number of person-years lived beyond that age by the number of people alive at that age. Age-specific death rates are used to calculate the probability of dying at a particular age. Although life expectancy at birth is commonly used, particularly as a measure of comparative health status, it is possible to calculate life expectancy at any age.