There is no normal bra size, every one differs. The average cup size however these days is a C whereas quite a few years ago it was a B cup. But you need to take into account plastic surgery when looking at statistics and I am not sure if the survey did that.
i think you mean average* and that would depend on how old you are. alot of girls are "late bloomers" like me and dont get them till your about 18. it runs in my family. some are exact opposite and get double Ds in highschool. everyone is different.
remember, boobs are made of fat. so if your real skinny and your small that has something to do with it.
the size all depends on your how tall and big you are..it varies from person to person.
i think B# is average (my gf told me so coz she is B)
There is no such thing as a normal bra size. period.