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The discussion on this infogram made me wonder about the number of PhD students that a full research professor successfully graduates in their entire career. By professor, I mean a full professor, not an associate or exclusively teaching professor or other positions referred to as professor depending on field and location. Of course, the answer is not a single number, but rather a probability density function that is a function of field, place, time, university, and probably other factors. To narrow the scope, I formulate the question as:

For selected fields and countries, what are recent figures on the mean and standard deviation (alternatively median and median absolute deviation, in case the distribution is non-Gaussian) for the number of PhD students successfully graduated per professor throughout their entire career?

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gerrit
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  • (I think the mean should be equal to the ratio of professors/PhD students at any instant in time, but I'm not sure) – gerrit Feb 26 '14 at 19:08
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    In the US, I would bet heavily that the median is 0. There are lots of institutions with no PhD programs at all. – Nate Eldredge Feb 26 '14 at 19:52
  • @NateEldredge But I would expect the professor in an institution (or even a department) without PhD students to be a teaching professor who teaches undergrads, not a research professor. – trutheality Feb 26 '14 at 20:16
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    @trutheality such distinctions are not so easily made. In many institutions I have seen in the US a research professor is someone who does not teach anything. There are a very small number of those positions in the US. On the other hand what you call teaching professors still do conduct research. Gerrit, how would you count a student advised by a someone while they were an associate professor? – BSteinhurst Feb 26 '14 at 20:54
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    Why exclude associate and assistant professors ? at least in the US, these are "real professors" too :) – Suresh Feb 26 '14 at 21:52
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    @trutheality:The US makes no such distinction as far as titles: a senior faculty member at Harvard and one at Harvey Mudd both get the simple title "Professor". For the US, a better measure would probably be for the denominator to include all tenured faculty at PhD-granting institutions, and for the numerator to count all students graduates over the professor's career (including those advised as an assistant or associate professor). – Nate Eldredge Feb 26 '14 at 21:54
  • I am guessing that someone could come at a reasonable guess using the data in the Taulbee Survey. – Irwin Feb 26 '14 at 22:12
  • @Suresh I exclude those in an attempt to get a more equal field between academics called professor in different countries. – gerrit Feb 26 '14 at 22:54
  • @BSteinhurst I'm not sure. Can an associate professor be the primary supervisor of a PhD student (I think they can't in Sweden, only secondary). – gerrit Feb 26 '14 at 22:55
  • @gerrit my advisor was an associate when I started working with him. It can happen. Where I was a student the issue was whether the adviser has tenure which usually happens at the same time as promotion to associate prof in the US. Exceptions apply. – BSteinhurst Feb 26 '14 at 23:31
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    @gerrit I graduated my first PhD student when I was still an assistant professor. Tenure status is simply irrelevant for PhD supervision in the US. (So getting stats about PhDs only from full profs in the US is going to be impossible.) – JeffE Feb 27 '14 at 09:17
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    I once heard (during a program review) that the "desired" number of students graduated is 1/year/faculty in CS. But I think 0.5 students/year might be a more reasonable number. – Suresh Mar 29 '14 at 20:38
  • So, the OP is asking if there are some statistics in some cases. (We can get plenty of opinions, anecdotes, and objections to the question.) So, if there are some statistics in some particular case, put it in an answer and say what the assumptions are. – GEdgar Mar 30 '14 at 15:00
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    How many grad students do you think a prof can supervise at once? In my PhD program, nobody had more than 5. I can't imagine a program anywhere that it could be 100. Let's say 10 as an order of magnitude. Now if that prof is active for 32 years, and each student takes 4 years, that means 80 students, right? So your actual answer is probably "between 40 and 160" if 10 was ok. But if 5 was ok, then as few as 20 - 5*8 and then halve it because not all profs are full force all the time. – Kate Gregory Apr 29 '14 at 22:40
  • @KateGregory: over here (Germany) while the professor is needed for granting the degree, PhD thesis does not need to have supervision. A hermit could write their thesis, and then knock at a professor's door and ask the professor whether they accept that thesis. The professor could then read the thesis, check Hermit's experiments and judge the scientific content and start the PhD-granting procedure (committee, reviewers, defense etc). In practice, supervision is often done by scientific staff ranging from habilitated scientists (have the qualification to be prof)) to postdocs. – cbeleites unhappy with SX Sep 05 '17 at 09:56

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It depends on the size and staffing needs of their lab. For example, theoretical computer science and mathematics professors may need no lab support at all. Thus, they are under no pressure to take grad students or post-docs and can choose just the ones that they want.

However, if you are doing work on stem cells, you may need a great deal of lab support. You would want a team of doctoral students and a couple of post-docs at any one time. In order to maintain continuity, you would want to accept at least one doctoral student each year. So if you had a 20 year career, you would have at least 20 students (or 20 - 7 = 13 given that it takes students 7 years to graduate and you don't want to leave students hanging at the end).

You'll need to narrow down what you mean by a "STEM" field in order to get a more precise answer.

RoboKaren
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My guess is that it probably varies hugely, by field, by department and then again by professor.

The fields might vary because of the different expectations about having co-advisors, the size of dissertation committees and so on.

Departments might vary based on their teaching needs. A department (Department A) that the university needs to cover lots of intro classes might be funded primarily by teaching, and so such a department is going to have a lot of graduate students. On the other hand, Department B that brings in tons of grant money might have more labs, but less teaching responsibilities, and therefore have a higher proportion of post-docs and lab assistants than grad students. Hence, profs at Dept B might have fewer students than profs at dept A, but that won't speak to the relative quality of the faculty at either institution obviously.

Finally, it might also vary just from faculty member to faculty member. Some people are jerks and nobody will want to work with them.

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    The question is very specifically asking for average numbers and statistics from different fields. I don't think this answer addresses the question. – ff524 Mar 30 '14 at 07:06
  • I agree with @ff524; while I'm not disputing the factual accuracy of anything in this answer, I don't think it provides any useful information that goes toward answering the question. – David Z Apr 29 '14 at 01:32