So the 4% of total number of farms accounts for 81% of value of all agricultural products?
Worse than the small margin is the variability. A good year can have a 50% margin and a bad year a -25% one.
Page down a couple pages on this PDF, and they have a great breakdown for each crop:
https://www.saskatchewan.ca/business/agriculture-natural-res...
https://www.ers.usda.gov/topics/farm-economy/farm-structure-...