The reason I'm asking is because my PhD supervisor "collects" - for lack of a better word - PhD candidates. She has at least 15 PhD candidates. None of them is being hired, except for one - as her private secretary. She also does not mind stringing out PhD duration by giving no input whatsoever but insisting that the research is still "weak" (without explaining how), and would let them go only after >5 years have passed. This makes me wonder whether the department receives money for each PhD candidate to finance the department, so that the PhD candidates' number and years spent there are of essence. I'm in Germany. We find the situation not ideal, but we are afraid to take this matters higher up, as we don't know if this might backfire. Is there anything to be done to get out of such situation?
This makes me wonder whether the department receives money for each PhD candidate to finance the department, so that the PhD candidates number and years spent there are of essence.
(Context: I'm familiar and have first-hand experience with the German system.) There is no direct flow of money for each PhD candidate. However, the number of graduated PhD students is seen as a performance metric for both departments and professors, and professors might receive a certain salary bonus for scoring well on that metric.
A rational reason for keeping around the candidates longer than necessary might be that she wants to squeeze more work out of them, including papers. There might also be other, non-rational reasons.
Is there anything to be done to get out of such situation?
Walk away. The advisor seems to have little to offer except for the dangling carrot of an eventual PhD degree; however, for a person that values their time as an asset that could be used for other things, that's probably not worth it.
There is nothing wrong with asking the question in a neutral manner to your administration or student representative.
I am not sure about Germany, but in France for instance, having doctoral students graduate on time (3 years) is considered a positive indicator for the department/university, and it is complicated for students to be funded beyond that - which has its own drawbacks. Some information can be found in HCERES reports, eg p7 of https://www.hceres.fr/sites/default/files/media/downloads/e2020-ev-0772710c-def-ped200021039-rd.pdf.
This is something that happens everywhere, and the extent of this depends goes beyond the funding model to cultural differences across disciplines and the personal style of the supervisor. Getting additional data points - is this a generic features in other groups around you or something specific to this supervisor ? - is important.
Beyond metrics valuable to the supervisor mentioned in another post, good students should be able to finish early and - if they have a constructive relation with their supervisor - will likely continue to work with the supervisor (at least in the short term) to finish papers. As a result, my experience is that it is rarely sign of a healthy group when students routinely overextend their degree.
I work at a German university and I assure you that profs do not get money for every PhD candidate. And to be honest, I have never heard of a prof having 14 PhD students doing unpaid work for them. Where I work, a prof usually gets the money for one or two young researchers - either a PhD student or a postdoc, or both. (This is why she is able to pay one of you.) If they want to have more, they themselves have to apply for third-party funded projects, e.g. from the Deutsche Forschungsgemeinschaft.
As competition is very high here, getting a third-party funded project is always a success, so profs that have a lot of PhD students are considered successful.
I think your prof does this to push her own career. If she has many PhD candidates, she can publish a lot with her name on it without having to do too much herself, and at the same time she at least pretends to be successful in getting funds. This is why she does not want to let you go.
If I were you, I would leave this prof as soon as possible.
Although I am not familiar with German system, I suppose this is the same as the other countries. Usually, not the departments nor the professors receive straight money per the time the Ph.D. candidates are there. (Although based on the rule of some universities the candidates are penalized after passing a certain time, this money usually is not paid to departments, it is mostly paid as university private revenue).
Anyway, Ph.D. candidates may have different indirect benefits: If they write more papers or receive more research grants from organizations it is beneficial; additionally, they may assist the professors to help other students; their longer education may show the professors' colleagues their seriousness and hardwork.
Another important reason can be the score that professors receive after educating each Ph.D. candidate. He may want to save this working score for his next year.
Or some professors just pass the times to get retired. They don't like to have more students and don't like to spend more time for their job. If their older students got educated, they might have to struggle with a new student.