As we get older, we repeat ourselves. I've said that before. Still, there was once a man who banged his head against a brick wall for 20 years: he suffered terrible headaches and everyone mocked him; one day the wall fell down. So here goes.

This is the season of good university guides. The UK is addicted to league tables, so the universities that prop up the bottom of the rankings are never listened to when they complain that they do not make sense.

You can see why the complainers are cut no slack: they want to be universities, so it serves them right if they are judged as if they were. You can't say on Monday that you are comparable with the University of Cambridge and on Friday that you never thought of yourself as the same sort of thing at all.

But since Cambridge and the University of Oxford tend to come top of the rankings, perhaps it is time that representatives of those august institutions stood up and pointed out how little sense the rankings make. This year, things will be worse than ever.

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The National Student Survey, which measures student satisfaction, will be factored into the rankings for the first time. As a result, figures that represent the subjective sentiments of those who are willing to fill in the forms will be turned into seemingly objective measures of the worth of ÖйúAƬ institutions.

This is not irrational, up to a point - the fact a university that in most respects is rubbish is much loved by its students is worth bearing in mind. But student happiness is a limited indicator of academic merit.

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I now repeat myself: "good" in this context means - if anything - either "good for" certain sorts of student, or "good at" certain sorts of thing. Is Oxford "good for" a student with few academic pretensions, but a strong wish to work in the hotel trade and a need for qualifications that will lead to employment by the likes of Marriott or Intercontinental? No. Should an institution provide what he or she needs? Certainly. Is a degree in tourism and hotel management a "real" degree? Why not? Is it comparable to a degree in physics? No. Would God prefer a world in which we all did physics? God knows, but we surely don't.

Now for the crux. Does the fact that Oxford excels at certain sorts of research help the undergraduates it admits? We always say it does, but it is not clear how.

How does a student studying French literature benefit from the fact that there are about 2,500 contracted research staff engaged in clinical research of one sort or another at Oxford?

Would the average Oxford undergraduate - 60 per cent of whom take humanities degrees - suffer if the university's medical school was transported to Slough? Its faculty would rather live in Oxford than Slough, but these guides are meant for potential undergraduates.

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So - to repeat myself again - what good does it do for an undergraduate intending to study French literature at Oxford if there are vast numbers of medical researchers at the university? If the answer is no good at all, why does it influence the rankings?

It may be of some use to the student that his or her teachers produce cutting-edge research in French literature. However, I doubt that it does more good than having teachers who do not push back the boundaries of knowledge, but spend most of their time reading the work of those who do and devote themselves to passing on the benefits.

Most cutting-edge research is specialised, and its direct benefit to the average student is not great. Being able to explain the difference its existence makes to the broader discipline is another matter entirely, suggesting that what we need are good scholars.

The best undergraduate education in the US is provided by liberal arts colleges. Their staff are released from the neurotic pressure of constantly refurbishing their reputations as leading researchers, but take seriously their responsibility to keep on top of their disciplines.

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The implication is obvious. The fact that Oxbridge students have three As at A level is irrelevant to whether Oxford is "better" than, say, Thames Valley University. League tables are nonsense because, for most of the students who attend either institution, the other would be a dead loss.

However, there are lots of interesting questions about value for money that could be measured. Given what it costs to attend any ÖйúAƬ institution in the country, will students, parents or the state get their money back, and then some? That really would produce a ranking worthy of the name. My guess is that it would be deeply embarrassing for most.

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A league table showing the cost to the punters, course by course, university by university, and how much difference ÖйúAƬ could be expected to make to students' lifetime income would be genuinely useful. And the politicians wouldn't be the only ones with red faces.