Why do people like to use average life expectancy? "Average life expectancy was 45 years old at the turn of the century."
That provides very little information about the distribution of lifetimes and provides a biased view when compared to the 85-year-olds mentioned in the next sentence. Infant/child mortality skews the average a lot. You could have everyone living to 90, if they survive to 5, and still have an average of 45. War and other disasters can also change the average in ways that have little meaning for the medical programs in question.
It also bugs me when people say "at the turn of the century," since we just recently had one of those but the person is talking about the one previous.
It's like it's a warm story that we propagate to make us feel great. As if we stand as demi-gods in comparison to the relative cavemen of 200 years ago. The most major accomplishment in respect to longevity appears to be... not letting our young perish. Which is obviously all well and good until this kind of argument is used to validify medicine perhaps beyond its merit.
This mistake seems to be getting more and more common.
I use the example of sea turtles - the average lifespan across a clutch of eggs is maybe 1 year - because one out of 100 survives. But the one that survives usually lives for 100+ years. The fact that the life expectancy at hatching is only one year tells you nothing about the distribution.
That provides very little information about the distribution of lifetimes and provides a biased view when compared to the 85-year-olds mentioned in the next sentence. Infant/child mortality skews the average a lot. You could have everyone living to 90, if they survive to 5, and still have an average of 45. War and other disasters can also change the average in ways that have little meaning for the medical programs in question.