That’s very likely true.

> one big difference is indoor air ventilation standards improved dramatically, leading to less spread of disease indoors.

I don’t know if this is. In 1975 air conditioning was much less prevalent, so people were much more likely to open windows. Buildings were also much leakier.

And it’s not simple as building ventilation has steadily improved, so teasing out the impact is almost impossible. In the 80s there was a big push for energy efficiency, so we went from 15 cfm/person in 1973 to 5 in 1981 then back to 20 in 1989.

But building envelopes also got much tighter, so there’s less uncontrolled ventilation.