Life expectancy is a statistical measure of the average, or mathematical expected value, of the remaining lifetime of an individual in the given group. For non-human organisms the term lifespan is often used to indicate the average length of life in a given species.
Notice that the life expectancy is heavily dependent on the criteria used to select the group. In countries with high infant mortality rates, the life expectancy at birth is highly sensitive to the rate of death in the first few years of life. In these cases, another measure such as life expectancy at age 10 can be used to exclude the effects of infant mortality to reveal the effects of other causes of death.
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2 Variations in life expectancy in the world today 3 External links |
Life expectancy has dramatically improved over the last few centuries of human history. These changes are largely the result of improvements in public health, medicine and nutrition. The greatest improvements have been made in the richest parts of the world, but the same effects are now spreading to other parts of the world as their economies and infrastructure improve. The major exception to this general pattern of improvement has been in those countries worst hit by AIDS, principally in Sub-Saharan Africa, which have seen significant falls in life expectancy due to the disease in recent years.
These improvements continue to confound the predictions of Thomas Malthus, who predicted what is now known as the Malthusian catastrophe which would occur when population growth exceeded the capacity of the world to sustain that population.
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There are great variations in life expectancy worldwide, mostly caused by differences in public health, medicine and nutrition from country to country.
There are also variations between groups within single countries. For example, in the US in the early 20th century there were very large differences in life expectancy between people of different races, which have since lessened. There remain significant differences in life expectancy between men and women in the US and other developed countries, with women outliving men. These differences by sex have been reducing in recent years, with mens' life expectancy improving at a faster rate than womens'.
The damaging effects of habits such as tobacco smoking and other addictions also make a significant difference to life expectancy.
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Life expectancy over human history
Variations in life expectancy in the world today
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