This is a bit of an amorphous question with tons of possible answers in some sense—e.g., the development of the scientific method—but actually identifying counterfactual benefits is tricky. The examples you listed probably don’t have major counterfactual benefits long into the future.
why not? smallpox might or might not have died out, but hookworm would still be around
Because if a given person didn’t solve the problem in year X, someone else may have solved the problem just a few years (maybe decades?) later.
Seems unlikely for these examples. It's not the scientific discovery that really matters; it's the public health program implementing it, which is a lot more sensitive to pre-existing conditions than discovering a fact about the world is.
One classic example is Benjamin Franklin, who upon his death in 1790
invested £1000 (about $135,000 in today’s money) each for the cities of Boston and Philadelphia: three-quarters of the funds would be paid out after one hundred years, and the remainder after two hundred years. By 1990, when the final funds were distributed, the donation had grown to almost $5 million for Boston and $2.3 million for Philadelphia.
(From What We Owe The Future, p. 24. See notes (1.34) and (1.35) on the WWOTF website here for references. Franklin's bequest is well-known but popular accounts are often slightly off in their details.)
Here's an NYT article from 1990 about the fight over the allocation of the funds after they had grown for 200 years.
I'm not sure what was done ultimately done with them, but according to Wikipedia Boston used it to establish and fund a trade school (I think at both the 100- and 200-year marks), the Benjamin Franklin Institute of Technology.
The rabies vaccine was another one that was developed in 1885 and improved human-well being for rabies diseases.
The example of rabies inspired a search for leading causes of death in the 1800s. Here's one article that sounded plausible for 1850 and 1900: https://nonprofitupdate.info/2010/10/21/10-leading-causes-of-death-in-1850-and-2000-2/
Another plausible stat from the United States from 1900 follows:
https://www.statista.com/statistics/235703/major-causes-of-death-in-the-us/
Prevention of a frequent cause of death from 1900 (such as pneumonia, tuberculosis, and diarrhea) sounds like a plausible clue to identifying an intervention that benefited many humans by 2020. One example that comes to mind from GiveWell's recent grant to Dispensers for Safe Water is water chlorination.
https://blog.givewell.org/2022/04/06/water-quality-overview/
Wikipedia claimed chlorination spread in the United States in the early 1900s.
Hello historians,
What are some interventions before 1920 that improved human well-being 100 years later?
For examples:
- Holden Karnofsky cited United States Hookworm reduction starting around 1909.
https://www.openphilanthropy.org/research/philanthropys-success-stories/
https://en.wikipedia.org/wiki/Hookworm_infection#Eradication_programmes
- Jason Crawford cited Smallpox inoculation before 1700 and vaccination starting around 1796.
https://rootsofprogress.org/smallpox-and-vaccines
More broadly, living conditions have on average improved enormously since 1920. (And depending on your view on population ethics, you might also think that total human well-being increased by a lot because the world population quadrupled since then.)
This effect is so broad and pervasive that lots of actions by many people in 1920 must have contributed to this, though of course there were some with an outsized effect such as perhaps the invention of the Haber-Bosch process; work by John Snow, Louis Pasteurs, Robert Koch, and others establishing the germ theory of disease; or Florence Nightingale pioneering the use of statistics in healthcare.