Well, the age of consent in Europe and the UK is all but universally set at 16. LGBTQ activists in the UK fought hard for that until recently, because while it was 16 for straight people, it was 21 for gay people.

But of course, setting 16 as legal for 18 year olds is not the same thing as setting it as legal for everybody. Laws like in Montana and Idaho don’t say anybody can have sex with a 16 year old, they say a 16 year old can legally consent to sex if their partner is not more than 2 calendar years older than they are.

This prevents tragic legal consequences for teenagers whose boyfriends or girlfriends are just a little younger than they are.