But such anecdotal observations are often subject to "survivorship bias": you see only those who have survived and not the 30-to-70 year olds who tried and die

But such anecdotal observations are often subject to "survivorship bias": you see only those who have survived and not the 30-to-70 year olds who tried and died: http://en.wikipedia.org/wiki/Survivorship_bias http://en.wikipedia.org/wiki/Survivorship_bias