HEALTH

  Life expectancy has doubled in all world region . What does this mean exactly? The term “life expectancy” refers to the number of years a person can expect to live. By definition, life expectancy is based on an estimate of the average age that members of a particular population group will be when they die. In practice, however, things are often more complicated: One important distinction and clarification is the difference between  cohort  and  period life expectancy. The  cohort life expectancy  is the average life length of a particular cohort – a group of individuals born in a given year. When we can track a group of people born in a particular year, many decades ago, and observe the exact date in which each one of them died then we can calculate this  cohort’s  life expectancy by simply calculating the average of the ages of all members when they died. You can think of life expectancy in particular year as the age a person born in that year would expect to live if the average age