I have to chuckle a bit with those who hold up "stats" as the be all. I clearly remember getting into an argument here about the need for snow tires once and provided clear indisputable statistics and some discounted them and said to drive slower.
Anyway back to Bears. How does the research know without doubt if the bear attack was merely a bluff and would not have led to injury or fatality. Because anybody with bear experience knows bluff charges are typical. If the bear wasn't going to seal the deal then often times a stick to the face or yelling at it would stop a charge. Nobody here is saying spray won't work at turning a bear most times. But most isn't all the time. I never carry a gun while baiting. I also never carry spray. The sound of an ATV and the cursing and bug swatting on the way in will move a bear off a bait. They usually don't hit baits mid day so that's s good time to bait.
The simple reality is if you are charged and everybody agrees that is a very very Low possibility the only way to guarantee you will stop the charge by a bear intended on killing you is to kill the bear. Spray just won't do that. In the end most people will never be in the situation to need to defend themselves. I have. I had to shoot a boar at point blank range that was climbing up my ladder stand to escape the sow trying to kill him. I put a bullet into him when his muzzle crossed the last step. He dropped like a rock and the sow gathered her cubs and slowly walked away huffing. An enraged bear is not a posturing or bluffing bear. I also made the point that virtually nobody has the nerves of steel to go digging for a weapon and that what is in your hands is what will save you wether that is spray, a .22 or a side by side 12g with 00 buck. Let's just say if I had to track a wounded bear I wouldnt have spray in my hands.