These two links seem to support what Nancy is saying about the numbers. They both indicate that the larger number of pure bred dogs come from backyard breeders.
Puppy Mills and Backyard Breeders vs Responsible Breeders - VeterinaryPartner.com - a VIN company!
Backyard Breeders & Puppy Mills : Tovik Siberians
The one mentions that the AKC stated that years ago, but I cannot find those stats. Will keep looking.
Actually, it makes sense to me. We all see puppy mills as being a problem because of the overwhelming amount at each facility. We do not see those amounts in individual homes, but the numbers of individuals breeding probably are astronomical.