17.3 about a sex

Plot: "The world average age for the first sexual experience... 17.3". Is that early? Late? Seno Sakura has a serious personality. Hara Tsumugi has never liked a member of the opposite sex before. Minagawa Yuna is experienced and is currently dating a company employee. At the age of 17, the girl's "sexual values" begin to fluctuate.