There are still a few lost souls who actually think that screenwriters have some authority. If only it were so. We have none. (I'm talking here about screenwriters, not hyphenates - i.e., people with two jobs, writer-directors, writer-producers.) There are lots of reasons. We're not, most of us, so terrifically talented. And we're so easy to fire - at least half of the people in positions of authority in Hollywood know the alphabet. You don't fire composers often; editors are safe too. But it's not unusual, despite what you see on the credits, to have two or three or eight writers write on one film script.