I went with 11, as I've always felt that a score of 10-11 is the "average" score people would start off with. Anything higher of lower than that would put you in the above or below average category.

I voted 12 mainly because 1) it seems like most published characters start out on average with slightly above-average stats, 2) in play yourself-campaigns we tend to give most characters scores in the 10-14 range (usually with Intelligence being the highest of the five), and 3) because I buy the argument that with the exceptions of random mutants, people involved in scientific experiments, or who acquired special devices, or were magically enchanted, etc., tend to be people who are slightly more intelligent, bold, healthy, or charming than the average person.