Mia, scientists would ALWAYS publish jointly with their supervisor, even if the research was 'just' the supervisor's idea and the student did all the work. I want to have three papers published, but so far have none...and I'm in my last year, so I'm hoping for lots of last minute results. I think ONE paper (in the sciences) per PhD is about the average, but there are people in my department who have published 11 papers - so sickening. That's theoretical work though (that makes it sound awful, but I'd admire them a lot more if they had published 11 experimental papers - I'm not even sure that wuold be possible).