diggy said:
There are valid aspects to both of those points, but they aren't the full story either.
Are you guessing or do you really know?
The reason I'm asking is that the "oversupply" in Ph.D. started in the late-*1960's*, and since they people have always been talking about the shortage of professors that have never arrived. We have several decades of experience as to why that shortage has not happened.
1) When a professor becomes 80 they are typically given emeritus status, which often comes with a TA salary. This frees up money for new professors.
Not true. Typically senior professors are money-makers for the department, and when a professor retires, they are no longer sponsoring grants or lobbying Congress, and so the income to the department goes down.
2) Departments tend to want to fill as many slots as possible. Its budget constraints from above that limit the number. Typically a faculty spot is established money, and once the position is vacated there is little conflict to maintain the money and begin a candidate search.
None of that is true. Departments have no reason to want to fill spots, and have good reasons for not wanting to fill spots. Faculty money is rarely established money. The other thing is that the costs of hiring a tenure-track professor goes way, way beyond salary. The TT professor will need funding for the next several decades, and there is a lot of overhead in spending on the equipment and support for the professor to do their thing.
Department budget happens year to year. whereas if you hire a tenure track professor, you are looking at substantial funding that will last for years if not decades. You just can't fire a tenured professor when money is tight (which is the definition of tenure). So in considering whether or not to offer a position, you have to think ahead at the funding situation for at least the next decade or two, and if funding looks like it is static or shrinking, people would prefer to just not hire.
Regardless of all of the details and 10-20% more or less slots opening up on a yearly basis, the "odds" of becoming a professor start around zero, go to 1/10 upon getting a Phd, and probably go to about 1:2-3 after doing a postdoc or two.
It really doesn't work that way.
I've seen people get teaching positions straight out of grad school, but yes, you (y'all) are correct that a PhD doesn't come with a complementary teaching position (or job for that matter).
So have I, but we are talking about research professors. It's not particularly difficult for a Ph.D. to get a permanent community college position, and it's trivially easy to be an adjunct teacher at a community college if you have a Ph.D. (basically you just show up). Small liberal arts colleges do have some hiring, but they hate hiring people that look at SLAC's as "the best I can do because I couldn't get a job at Princeton."
Something that made working as an adjunct a lot less attractive was when I was in a supermarket and the person bagging the groceries mentioned that he needed some time off the next day, because he had to teach a class at Austin Community College. (Dead serious, this actually happened.)