In the video below Hank Green does a good job of addressing one of my hobbyhorses, namely the popular misunderstanding of life expectancy.
Current U.S. life expectancy at birth is about 76.5 for men and 81.2 for women, but if you're an American working out when to start collecting Social Security, those averages are misleading. They include people who die in childhood or as young adults or in middle age. Once you reach, say, 65, you're obviously not going to go back and die younger. According to the Social Security Administration, at age 65 American men live an average of 19.3 more years, until the age of 84.3. American women at 65 average another 11.6 years, reaching 86.6.
You occasionally hear that when Social Security was first set up with a default retirement age of 65, most didn't live to be 65. That's true only if you include those who died before reaching adulthood and paid little or nothing into Social Security. Even in 1940, when Social Security payments began, a majority of Americans who reached 21 lived long enough to draw Social Security benefits. And while retirees are living longer today, remaining life expectancy at age 65 has risen only about five years since 1940. (There's more on life expectancy and Social Security on the Social Security Administration website.)
A major reason life expectancy at birth is so much better today is the tremendous reduction in childhood and infant mortality, largely thanks to vaccines, antibiotics, and improved sanitation. Giving birth is also much safer for mothers than it used to be.
I suspect most people don't fully realize how many children used to die as a matter of course. Disasters typically happen suddenly and attract notice, while good news, even astoundingly good news such as saving the lives of untold number of children, is more likely to develop more gradually and pass unnoticed.