Thanks to my NEHGS newsletter, I can point to where my own observations are confirmed (and explained) in print. The Summer 2014 edition of the Old Sturbridge Village Visitor reports on some historical myths, one of which is that everyone died young in the olden days. I get so frustrated when people attempt to explain something in the past by invoking, "because they only lived to be 40 years old." Many of my ancestors lived into their 70's, 80's, and even 90's. Here's the explanation:
While average life expectancy was shorter in 19th-century New England than it is today, many people then lived into old age, and some even lived beyond 100 years. The Bible says that expected lifespan 3,000 years ago was "70 years; 80 for those who are strong" (Psalm 90:10). But before the mid-20th century, people died regularly in all stages of life, not just in old age. Life expectancy at birth in early 19th-century New England was only in the mid-40s.
But as the old saying goes, "there are three kinds of lies: lies, damned lies, and statistics." Statistics in the 19th century were skewed by high childhood mortality rates—especially in urban areas—largely due to infectious diseases such as pertussis, measles, scarlet fever, and diphtheria. (Thanks to vaccination, these diseases are rare today.) By the time a person reached age 30 his life expectancy jumped to 67 and the average 50-year-old could expect to live until age 73.
Note that this still puts many of my ancestors above average, but that's no surprise. :)
Another statistic: Productivity for a person 40 years old in the days before television would be equivalent to 80 or more today.