Well, I'm in Britain, and in Glasgow people generally break their virginity at around 13/14. Some people wait, some people don't.
I know a 21 year old that's still a virgin, it's just that generally it's not considered a big deal. Sex is made out (mostly by religion) to be a big deal and this is reflected in the law. Now, I'm not saying that kids at the age of 13 should be running around having sex, but it's when there's a ban on certain aspects of sex education and a stigma about sex, the figures for teenage pregnancy tend to rise among other things. People under the age of 16 in Britain have sex all the time, it's only really a big deal when they haven't been educated enough to learn to wear a condom and such.
And I think also, compared to other countries the children here maybe aren't as sheltered as most. We tend to grow up fast. (I don't consider that a bad thing).
However, I have a friend that's now been placed on the sex offenders list because he had sex with his 15 year old girlfriend (he's 19) which I think is ridiculous, considering they've known each other their whole lives and have been dating for a year. He's on the run right now and no one knows where he is.