You shouldn't be "bear"-ish with RFK, Jr.

It does not adjust, so comparisons to long ago are not quite right. But 2019 working age population is only a bit less than now. Still, you have to look back before the dot-com bust in 2000 to find much lower rates of long term unemployment.

You might find some leads in the work of Stephen Stigler, such as his book `The History of Statistics`. You can browse some of it on Google Books.