To what extent are parents responsible for their children's behavior?

We can think of this at various ages. In early life, if the child is very polite, or if the child throws tantrums constantly—do parents get credit or blame? In the middle years, the children bully others, or they do their homework every night and take care of all their responsibilities without being asked: do parents get credit or blame?

As teens, they get a job, drive responsibly, and work for a charity of some kind or start a business, or they get pregnant or develop a drug or drinking problem: what blame or credit to parents get?

Late teens, early twenties: they get through college, or find a job, and start taking care of themselves, weaning themselves from their parent’s help; or they can’t seem to do anything for themselves, stay at home, don’t even pay rent, and seem to lead a slacker life. Who gets the credit or blame—the children or the parents.

Obviously, this isn’t a black or white issue. It makes sense to apportion responsibility between the parties. I’m really curious as to how people think about this.