I am wondering whether there are some available sources for statistics on the average number of PhD students and postdocs by Professor/supervisor across different fields, universities or countries?
I have the impression that some fields/universities favor a "chair" or "lab" system where one Professor supervises a large number of PhD and postdocs students, whereas others have a more "department" style with more Professors, but I haven't found any data/study that discusses this aspect?
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