The research that has been cited for the 80-20 informal-formal is NOT, in my quick reading, very compelling. I say this despite finding that lots of what I've seen in organizations shows lots of informal-learning.

BUT here is the key thing which the 80-20 rule leaves out--EVEN if it is true--THE QUESTION IS: Not whether this large swath of informal learning is there, BUT (1) whether it is modifiable, (2) whether WE can actually modify it, (3) whether it is cost-effective to modify it, (4) AND whether modifying it produces benefits that outweigh the costs.