Interesting question, and very variable. Things like curfews depend a lot on the relationship between parents and children, if you trust your child enough to not do anything silly, then a curfew can be quite late, but if trust is an issue it's better to keep the curfew early to make sure they are following the rules.
Another big factor is gender, I know from a lot of friends, that girls when trusted by their parents will be allowed to stay out to quite early hours of the morning. On the other hand if they are known to get up to mischief generally have an early curfew. For boys curfew can be pretty late, many parents give there sons a sense of independence by giving them longer curfews.
Another major factor is the safety of the city you live in, and the location of where your kids will be.
I live in Shanghai China, when I was 16, my curfew was 12, my parents felt very safe with that because I live in City that is relatively safe, I can walk down the street at 2am and no one will bother me. But if you live in city, that's known for things happening after dark an early curfew would be better.
I hope this answers your questions!