Unfortunately if it is truly exponential it should go much lower, 60%. That's what exponential means:)
Too many people throw in numbers that are absolutely wild guesses. New managers tend to believe what is said in here.
1. Exponential can mean anything (about 98% of training would be straight proportional).
2. No one except the BBs can confirm that. And they have not been willing to blab out that for some years now.
3. Personally I cannot believe that it has such a great effect. 47 minutes sound ok for me. But it tends to be less than 98% of training.