I think that the number of people who have substance abuse issues is much higher than statistics show. Think about it, for every person that admits that he or she has a problem there is a huge hand full of others who have a problem but are putting on a smile and claiming they are fine.
Don't try to wrack your brain trying to figure out what "normal" drinking is. It is just not worth trying to figure out who is a normal drinker and who is not.
It is prob. better to avoid places where there is extremely heavy drinking going on. There is no reason to put yourself in a situation where there is temptation, plus being in a place full of drunk people sober is not exactly what many people would call a good time.