But sometimes averages don’t just blur an underlying reality, they obliterate it. I’m amazed, for instance, by how many perfectly smart people seem to believe that the 47.3-year life expectancy in 1900 is synonymous with “most people lived significantly shorter lives back then.” I suppose they picture our ancestors, in their mid-forties, tottering around with canes and false teeth and trying frantically to get their affairs in order. From this perspective, the passage of the Social Security Act in 1935 would have been a cruel joke indeed—Yes, you can start collecting retirement
This is a great explanation, but it begs the question of why we keep using "average life span"
