With respect fuckingmoles and zeezeek, I'm aware that uni lecturers are fond of saying that their students are thicker than ever. That's not really what I was after. In particular, I don't think it's possible to get a good sense of any shift from comparing one's own experience as a student with one's own experience as a lecturer. I'm wondering if anyone has actually done any research into the subject.
Maths superficially seems like a good comparison, but again it's very hard to say that students are getting worse there.
I know for example that it's fairly rare for state school kids to be able to study maths at Cambridge unless they are a bona fide genius - most state schools just don't teach enough maths for them to do the course well and many only have provision for students to do one maths a-level, whereas private schools will let their kids do two or three maths a-levels (maths, further maths and further further maths), often on top of other subjects. Thus, privately educated people who are good at maths end up being better at maths than state educated people who are good at maths, simply because they do a lot more of it.
So an economics professor noticing that students generally have worse maths these days may be noticing this due to a general decline in maths teaching. But they could also be noticing this due to a general improvement in teaching in state schools, which is enabling more and more state educated students to get the grades necessary to do economics at a RG university. However, since these state educated students will mostly only have one maths a-level, they may well have a lower level of maths than the privately educated students who previously dominated the course. That doesn't, of course, mean that they are worse than those students, just that they haven't had the same opportunities.
Thus, economics students getting worse at maths could just as easily be a sign of the raising of standards than the lowering of them. This is why anecdotal evidence isn't helpful.