Life expectancy

Life expectancy is a statistical measure of the average time an organism is expected to live, based on the year of their birth, their current age and other demographic factors including sex. The most commonly used measure of life expectancy is at birth (LEB), which can be defined in two ways: while cohort LEB is the mean length of life of an actual birth cohort (all individuals born a given year) and can be computed only for cohorts born many decades ago, so that all their members died, period LEB is the mean length of life of a hypothetical cohort assumed to be exposed since birth until death of all their members to the mortality rates observed at a given year.

According to data compiled by the Social Security Administration:

  • A man reaching age 65 today can expect to live, on average, until age 84.3.
  • A woman turning age 65 today can expect to live, on average, until age 86.6.

And those are just averages. About one out of every four 65-year-olds today will live past age 90, and one out of 10 will live past age 95.

There is a strong link between mortality and IQ: higher intelligence means, on average, a longer life. This relationship has been extensively documented by Ian Deary and his colleagues at the University of Edinburgh using data from the Scottish Mental Surveys. In 1932, the Scottish government administered an IQ test to nearly all 11-year old children attending school on a single day. More than sixty years later, focusing on the city of Aberdeen, Deary and colleague Lawrence Whalley set out to identify who from the cohort was still alive, at age 76. The results were striking: a 15-point IQ advantage translated into a 21% greater chance of survival. For example, a person with an IQ of 115 was 21% more likely to be alive at age 76 than a person with an IQ of 100 (the average for the general population).

It has long been the case that better-educated, higher-income people enjoy longer life expectancies than less-educated, lower-income people. The causes include early life conditions, behavioral factors (such as nutrition, exercise, and smoking behaviors), stress, and access to health care services, all of which can vary across education and income.