This article is also posted on my blog.
Update 2021-05-09: Upon checking data more carefully, I have revised the chances of becoming a professor in math.
A grievance expressed by some PhD students and Postdocs is that science works like a pyramid scheme: Young scientists are encouraged to invest into building scientific careers although the chances at remaining in science are extremely slim. ... The super-prolific authors at the top of the pyramid ... are usually heads of large institutes with many subgroups and large numbers of PhD students, while the bottom of the pyramid is populated by PhD students and Postdocs ... A new index, the Ponzi factor, is proposed to quantify this phenomenon.
The author of the article is named as Charleeze P. Ponzi, which is also the name of the person who invented Ponzi scheme. Since it is unlikely that the ghost of Ponzi (died in 1949) who wrote the article, perhaps the article is meant to be a joke.
However, the author does have a point in saying that "the chances at remaining in science are extremely slim". Take mathematics as an example, according to American Mathematical Society's latest annual survey, during the 2017-2018 academic-year
In mathematical and statistical sciences, 1,960 PhDs were awarded by the responding departments ...
Meanwhile, during the same period,
985 tenure-track positions in mathematical science
were offered across USA, among which 775 positions were filled. However, among these positions, only 296 are from departments offering PhD degrees, i.e., from places where you are supposed to do a lot of research besides teaching. And these numbers have been relatively stable for years. Thus, roughly speaking, a math PhD student in USA has at most 40% chance of becoming a tenured professor, but only 15% chance if you also want do a lot of research besides teaching.
15% does not sounds too bad.
But I probably overestimated this number, since PhD of other majors, like myself who studied Computer Science, applies jobs in math departments. And PhD produced in other countries also compete for these positions.
These numbers only applies to USA. It is likely that in less affluent countries there are not as many positions. For example, when I applied a position in Sweden, there were around 40 applicants in total.
Moreover, the situation of the whole field of natural science may be bleaker. By one estimate, about 2.2% German PhD students in natural science become professors.
I used to joke to PhD students that they should strongly recommend their friends to not to do a PhD, because
- research is indeed hard;
- this reduces competitions they fill in future job market.
However, I do seriously think people should think twice before they apply for PhD positions. They must realise that it is unlikely they will become professors. So, before applying, instead of imagining themselves becoming the next Einstein, people should think very hard about how doing a PhD can help them getting jobs outside the academic. Otherwise, five years of hard work may lead to nowhere and the result can be devastating.
That being said, I think Sweden, where I did my postdoc, makes studying for a PhD less risky. First, in Sweden, university only accepts PhD students whose funding has been guaranteed for fives years. This protects students from running into financial difficulty when they are close to finish line. (When I studied in Canada, a fellow PhD student had to use GoFundMe to support himself during the last year of his study.)
Secondly, PhD students in Sweden earn about 30k SEK (3500 USD) per month, which is not much but enough to have a reasonably comfort life. Thus, for most of students I met in Sweden, graduate school is just a place where they can explore their intellectual interest without worrying about their financial situation. They enjoy their time and they get well-paid industry jobs in the end. For me, that does not seem to be a bad deal at all.
Maybe other countries can learn a bit from Sweden. And maybe you can consider doing a PhD there.