Just the same way that young english women should technically stay virgins until they reach the legal age of 16, (12 in some parts of Manchester though)
So for chinese women, its the no-sex-before-marriage tradition? Truth is, a close friend of mine was telling me the other day that many overseas female student from asia - in particular from china or japan, are very rarely in relationships. So thats what made me wonder if these young females from china remain single and therefore virgin as part of their tradition.