It's not that the details are not known. Bahram Bekhradnia, head of policy at the Higher Education Funding Council (England), has demonstrated that drop-out rates are almost linearly, but inversely, related to A-level scores. There are also correlations between student attainment at entry and both social class and whether one attended a selective school.
The omission of the vital entry data denies us the opportunity to make sense of the other numbers and see higher education as it really is.
We thus have the absurd situation of the University of East London being celebrated for widening access, but shamed for massive drop-out, while Cambridge is berated for apparently showing social class and school bias, but applauded for its high completion rate.
With entry qualifications included, it would immediately be obvious that Britain has been trying to do the impossible in higher education: to move to a mass system by merely scaling up something designed for a selected few.
The old British university system controlled quality at the point of entry and, through a high threshold, was able to educate students to a high standard in a short period of time with few drop-outs. In fact, some higher education had been transferred to the sixth form (and hence some of the complaints about the specialisation of A-levels). Because only small numbers were involved, the taxpayer could afford to be generous and meet not only fees but living costs.
It worked wonderfully well for those chosen, but failed the other 90 per cent. It was therefore wholly right to create greater educational opportunity; but wholly wrong to assume that this could be achieved by scaling up what was already there.
The consequences come tumbling out of the tables in spite of obscurantism. The universities are being asked to take a much wider ability range, less well-prepared, and keep up completion rates at the old degree standard, still within three years - and all on less money. They are also under financial pressure to fill all their places.
With 60 per cent now going on to university at some stage, the taxpayer is no longer able to meet all the costs and the Government has had to scrap maintenance grants and introduce tuition fees. Students without financial support from home, and admitted on lower entry qualifications, have to keep up with their courses and hold body and soul together.
Clearly something has had to give. Students are drawn in, faced with unrealistic demands and then spat out. But it is likely that the standing of the degree is suffering also. If universities are to be hauled over the coals about drop-out rates, it is only natural that they should be tempted to massage them down by lowering requirements.
Sooner or later the Government will have to stop batting on about inclusion, postcodes and selective schools, and address the essentials of real higher educational opportunity; the chance to engage in high-quality advanced learning. The Open University has been marvellously successful in showing how open access can be squared with top-class achievement.
The key is flexibility. The present Government seems to want to tie the universities in a straitjacket. It appears to want them to operate to the same qualifications and standards, to have the same lengths of courses, to have the same social mix, and to charge the same fees. It should have the courage to stand back and allow them to develop in different ways.
The universities should be left to concentrate on identifying and developing talents, free from the silliness of the Quality Assurance Agency. They should be allowed to develop courses of different lengths to meet different needs and, crucially, they should be permitted to price their courses to generate income. The Government could secure the state's interest through, say, merit scholarships and grants for the socially disadvantaged.
The present system is so obviously out of kilter you would think the Government was bound to act soon. But the signs are not good. Its statistics seem designed to conceal rather than reveal. The performance indicators which it has allowed the HEFC to publish, minus entry qualifications, seem more about distracting us with bathwater than giving us a good look at the baby.
The writer is Sydney Jones Professor of Education and the Director of the Centre for Education and Employment Research at the University of Liverpool