Steve Herrero from the University of Calgary looked at different scenarios where hunters or hikers had encounters with grizzly bears. The hunters usually had firearms to deter the grizzly, and hikers or hunters had bear spray to use in their encounters. The firearm portion of the study looked at 269 cases, out of 444 hunters. The bear spray study looked at 72 cases, out of 175 people.
From those numbers 98% of the ones using bear spray walked away unharmed, and no bears were killed. With the firearms, 56% of the people were injured and 61% of the bears were killed. One difference may be that the encounters were more dangerous. These numbers should be enough for some to start carrying bear spray, if they aren't already during hunting season. From WausauDailyHerald.com .