Why do past PhD exams appear more difficult than current ones? I noticed while doing practice math PhD exams that the newer exams tend to be a bit easier than the older exams. The online archive goes back about ten years or so, but I was able to dig up some old exams from the mid-80s. I was absolutely shocked. I would get wrecked if they gave me one of these. I don't even think I could finish one if they let me take it home.

I looked around at some other PhD exam records at other universities, and it seems to be an across the board thing, not just my department.

Some people I've asked about this give the explanation that PhD programs are bigger now than they used to be-- in other words, in the past, only geniuses got PhDs, and since then cretins like me have gradually wormed our way into academia and lowered standards for everybody. This would make sense, but I'm not sure if this is just something people say, or something that is actually true. People have a tendency to put the past on a pedestal, and I'm skeptical.

Another explanation I could think of would be drift in material content. Maybe they were studying different stuff back then at the same difficulty, or using different terminology to study the same thing we do now. Maybe it just seems harder to me because I'm not used to how they talk about it. A lot of PhD level material is, after all, reasonably modern.

I also wonder if exam practices used to be different-- open book, take-home, more hand waving tolerated in grading, offered at the end of the 5th year. Something?

All this is speculation, though, which I find unsatisfying. Has this actually been studied with healthy rigor and skepticism? What is the history?
(In mathematics:) I'd be willing to believe that pre-college math curricula, and lower-division college (in the U.S.) curricula have become easier to get through, for reasons mentioned in other answers and comments. But I think this becomes less universally so at upper-division level (last two years of undergrad in the U.S.) and even less so with regard to the sort of &quot;prelims&quot; that math grad students typically do/take in the first year or two of their graduate work. This reflects my observations over the last 45 years in math in the U.S.
So then how to account for the phenomenon apparently observed by the questioner? Again in my own direct experience, decades ago there were impulses to ask &quot;interesting/challenging&quot; questions on prelims, that even the other exam-writers might not be able to do. Some contest-like spirit, resembling the old Tripos in the UK? At the same time, again somewhat contest-like, the questions were at a lower mathematical level than nowadays. This, combined with the impulse to ask challenging questions, led to many Baroque, Rube-Goldberg-like questions whose statement alone might be difficult to parse, and whose relation with any known mathematics was unclear. E.g., very complicated questions about iterated operations in point-set topology, with delicate separation assumptions? Difficult questions about proving that a bunch of relations in a group implies another one?
After a decade or so of that kind of thing, it was apparent to me that such exams did not encourage forward-looking study on the part of the students, which was a bad thing. Often, as in prep for contests, some amusing tricks were learned, but basic, standard, useful more-advanced ideas were neglected entirely because they'd never show up on those exams. Thus, around 1989, we deliberately changed the nature of those exams to address less-tricky, higher-level mathematics that would actually be used by people in doing their PhD work. Another attitudinal change has been within the last 10 years, when we have moved completely away from surprise/tricky questions at any level.
At least at my own University, it's not at all the case that basic graduate education is being diminished in favor of supposedly jumping into research immediately. As in some comments above, it's not feasible to really start doing modern mathematics research while not knowing anything... But, yes, we do try to encourage a more active version of engagement than merely &quot;fulfilling requirements&quot; (even while those &quot;requirements&quot; are aimed to be useful).
So, in the end, I'd argue (as in other comments) that the exams are not truly easier, but just &quot;modernized&quot;, so that some acclimitization to modern mathematics makes them seem easier in our context.
(And, yes, I recognize that in fact some grad programs in math have &quot;thinned&quot; their prelim requirements, apparently motivated by &quot;getting students into research faster&quot;, but it is not clear to me that this can truly accomplish the avowed goals... though I am equally confident that programs would be disinclined to candidly discuss such a thing. The ever-increasing commodification of &quot;research&quot; does provide considerable pressure to degrade things...)