I don't know about the percentage part, but I would agree with this. If you are a drinker at home, then you are most likely going to be a drinker on the trail. If you abstain from drinking at home, or rarely drink, then chances are you will probably do the same out on the trail. The exception may be if you are around other hiker's who decide to have a party and you decide to party also, or you decide to head into town to a bar or a restaurant where everyone else is drinking and you join them. The people who would be considered steady/heavy drinker's are going to continue drinking regardless of their location as long as they are able to locate and obtain it.