Life expectancy is an indicator of how long a person can expect to live on average given prevailing mortality rates. Technically, it is the average number of years of life remaining to a person at a specified age, assuming current age-specific mortality rates continue during the person's lifetime.
Life expectancy is a common measure of population health in general, and is often used as a summary measure when comparing different populations (such as for international comparisons). For example, high life expectancy indicates low infant and child mortality, an ageing population, and a high quality of healthcare delivery. Life expectancy is also used in public policy planning, especially as an indicator of future population ageing in developed nations.
The expected length of a life is inversely related to the mortality rates at that time. In Australia, life expectancy has increased significantly over the past century, reflecting the considerable falls in mortality rates, initially from infectious diseases and, in later years, from cardiovascular disease.
Based on the latest mortality rates, a boy born in 2006 would be expected to live to 78.7 years on average, while a girl would be expected to live to 83.5 years. However, a man and woman aged 25 in 2006 would be expected to live to ages 79.7 and 84.2 years respectively. This shows that once people survive through childhood, the chance of dying as a young adult is very low and hence life expectancy increases.