First, a few facts. In the last 100 years, life expectancy at birth in the United States has risen by about 20 years. Granted, that good-news story has darkened quite a bit lately, with the COVID pandemic and drug overdoses claiming the lives of too many Americans. Even so, the expected life span of a baby born in the U.S. today is 77.5 years. For 1923 babies, it was 57.2.