Found this cool site that shows the breakdown of job titles over the past 150 years in the US. If you type in “farm” you can see that the percentage of the population employed as farmers and farm laborers has dropped from ~50% of the population when the Civil War was being fought to ~2% today although it looks like the decline has substantially slowed since the 1970s.
If you type in scientist you can see the post WWII explosion in the scientific professions to the point where today one in every three hundred (one third of one percent) working americans can claim that title. Which really is a major increase.
Matt pointed out in my post on Agricultural R&D that one of the reasons investment in research has dropped some much is that farming as an occupation has shrunk, giving farmers less electoral clout to advocate for publicly funded plant breeding, studies of plant pathogens and university outreach.