Comment by GTP

You're right, running now a farm that is profitable and can stay on the market is very different from doing so 200 years ago. But knowledge is just one aspect. The other aspect I mentioned is having less people in the field than what the market asks for. In the specific case of farmers, I think that modern farms are so much more efficient that we need way less than before, even if the world's population grew. So, while there's a gap between the knowledge required and the earnings, I think this can be explained by farms having a much greater output now, and so the market doesn't ask for more farms than what we have. This could be false at a global scale, but I think it is true at a country-level scale in most of the developed countries. Hence why farmers aren't paid much in those countries.