> Have you taken an oral exam?

I have, yes. My university experience ran the gamut, in that I had both classes in a massive lecture hall of hundreds of students where most never spoke a word to the professor and all exams were done via scantron, as well as small graduate courses of around 4 students where the entire class was oral exams and one-on-one demonstrations and group discussions. The smallest course was only available at all because of a particularly passionate professor who insisted on holding it, and the class was never available during semesters where he wasn't available, because nobody else was willing to put in the work to personally administer the class. Notably, all those courses cost about the same amount of money per credit hour from my perspective, so the university was making orders of magnitude more money on the large class (where I can't see oral exams being feasible without significant investment) than they were making off the small class.

> You can delegate to grad students, but the same can be said of oral exams

It's much harder to delegate an oral exam than a written one. As you've mentioned, oral exams combine administration with grading, which means the grad students who are delegated to need to be able to administer the exam (ie, effectively probe the knowledge of each examinee) as well as evaluate their responses. In a written exam, the grad student only needs to evaluate the responses, usually against a set of predetermined criteria since the structure of the questions is set in stone.

None of what universities are moving towards is better, but I fail to see how it isn't cheaper.

Another factor is in the USA, at the undergraduate level, there is a strong incentive for "professors" (more assistant and adjunct than tenured) to grade in a manner which is totally rationalizable and consistent between students. Administrators call students "customers" who are buying a degree; if a student doesn't like their grade they will complain about it, and if the teacher hasn't explicitly formalized their grading process they will be in hot water. So for example asking different probing questions of different students might lead to accusations of arbitrary and capricious grading. It encourages checklist-style rubrics for grading. Obviously one could formalize a decision tree for more loosely structured oral exams but that's significant effort.

A rubric is as easy to apply to oral exams as a written one and that is generally all that administrators would like to see. Any interpretive exam is going to run into accusations of arbitrary and capricious grading.

I'm not disputing your point at all, but an interesting thing that happened at my school was that we weren't called "customers" but rather the president of the school would refer to students as "commodities". For a long time they'd treated us as such but hearing this was the blatant example of it.

> asking different probing questions of different students might lead to accusations of arbitrary and capricious grading

But what if AI conducts it?

At my university in Germany the trade-off is at approx. 50 students in a course when written becomes much more efficient. I can take max around 12 oral exams a day mostly it is rather 8.

The point is that the written exam is largely outsourced to PhD students here. The professor only looks at the model solution before and the grade distribution afterwards in extreme cases. Also you can parallelize the grading so that even for 300 students the grading is done in a week. Typically the professor spends half a day otherwise it would be 2 month...

I only do oral exams for my course and I am very happy how well it works. I normally ask students to grade themselves afterwards and I am typically spot on (I have written down the grade before).

That's the bottleneck though. It's not on the students end. It's on the professor/instructor/grad student end. It's not uncommon at big universities to have classes with hundreds or even thousands of students. Even if the oral exam can be completed in half an hour and there's 10 professor/instructors/grad students that can evaluate them that's STILL 50 hours each in a class of 1000 students. With a written exam it's one two or three hour writing period, then marking. Some of the huge classes will do multiple choice only on Scantron sheets so marking is literally done in minutes. With the courses I've marked it usually takes much less than half an hour to mark an exam on average even if it took the student 3 hours to write.