Year in, and year out, the ratio of dogs to favs covering the spread is always around the 50/50 mark.
There are few exceptions.
Phoenix,
I hope you don't think buddy discovered that thought on dogs? It has been around forever, and although it sounds great, it is still a coin flip as to which dogs get the cover, and which lose!
The fact is, if dogs covered all the time, we would all be rich, or stupid to not be!
You would be better served to see who has the most wins (Fav/Dog) towards season's end, and go the other way, in hopes of that "50/50" split we always see.
There is no rhyme or reason as to what happens in this game, as far as these things go.