Here is a good discussion on some common errors in the use of life expectancy data - such as mistaking period life expectancy (a statistical measure of health and medical technology) for cohort life expectancy (how long people actually live). It doesn't touch on the great uncertainty in predictions of future longevity due to the rapid pace of development in biotechnology, but is still an interesting read: "The US Government estimated its population had a life expectancy of 78.5 years in 2009. If you type 'life expectancy' into Google, it will spit back the World Bank estimate of 78.2 years in 2010. You've likely read numbers close to these in textbooks and articles. But what do these numbers actually mean? You might guess from the first that someone born in the United States in 2009 could be expected to live about 78.5 years. This is not the case! It actually measures how long someone would be expected to live if every year of their life was spent in 2009. In other words, there is no accounting for progress that decreases mortality rates. And that's on purpose. It is what is known as a 'period life expectancy'. Period life expectancies are used to track the general health of a population. With them you can easily compare one country to another. You can also monitor general population health over time. But the number you want if you'd like to know how long people will actually live is known as a 'cohort life expectancy'. It measures how long someone born in a particular year (a cohort) can be expected to live. It is also not in the US Government yearly mortality report for 2009. The reason is that we won't know it until everyone born in 2009 is dead! That will hopefully take a long long time."