The average American born in 1900 could expect to live less than 50 years. Today’s US life expectancy is roughly thirty years longer, and continues to rise. Why has life expectancy risen so much over time?
The figure below describes changes in US life expectancy over the 20th century for men and women. Data come from Noymer and Garenne.1
Life expectancy rose fastest in the early part of the 20th century. This represents a continuation of rising longevity over the late-19th century.2At the outset of the century, diseases like diarrhea, tuberculosis, pneumonia or influenza caused many more premature deaths. Infants and children were far more likely to die, and much of these life expectancy gains were the result of more people making it to adulthood. Adults could expect to die at a younger age as well, but the difference was less stark. Life expectancy rose as the result of several developments, like the development of clean water systems, vaccinations, better housing stocks, antibiotics, better food yields and more stringent food regulation (e.g., making it illegal to sell spoiled food).3
Over time, the pace of life expectancy slowed. Falling infant and child mortality rates helped fuel the more rapid rise in life expectancy in earlier decades. Arguably, this was lower hanging fruit. With the passage of time, longer life spans were a matter of delaying death among the elderly. Presumably, there are natural limits to the amount of time that humans can live, though it is uncertain how close we are to those limits today.
- Andrew Noymer and Michel Garenne (2000) “The 1918 Influenza Epidemic’s Effects on Sex Differentials in Mortality in the United States”Population and Development Review, 26(3): 565 – 581. Figures from 1918 show an implausible, one-year drop of over ten years, and are recoded as missing. Data available for download athttp://demog.berkeley.edu/~andrew/1918/figure2.html↩
- J. David Hacker (2010) “Decennial Life Tables for the White Population of the United States, 1790–1900” Historical Methods 43(2): 45-79.↩
- David Cutler and Grant Miller (2005) “The role of public health improvements in health advances: The twentieth-century United States”Demography, 42(1): 1-22; Laura Helmuth (2013) “Why are You Not Dead Yet?” Salon, Septemberhttp://www.slate.com/articles/health_and_science/science_of_longevity/2013/09/life_expectancy_history_public_health_and_medical_advances_that_lead_to.2.html↩