I sent an e mail to Dr. Rollins at the quail research center asking that question. If he responds to my e mail I'll post his opinion. I've always heard 80% also. I figure his opinion would be closer to the truth.
There is time, and you must take it, to lay your hand on your dog's head as you walk past him lying on the floor or on his settle, time to talk with him, to remember with him, time to please him, time you can't buy back once he's gone" GBE