"Coalition failed to heed Ucas' AAB warnings" (News, 20 September) does not address the most serious issue arising from the government policies introduced for 2012-13 entry. It was always recognised that there would be a "squeezed middle" of universities that would lose AAB+ students to their more popular competitors and not be able to replace them because of student number controls. However, the 6,000 shortfall in AAB+ students means that the squeezed middle includes more institutions than might have been expected.

The squeezed middle has lost quota places to the core-and-margin policy, which has further reduced its ability to make up for fewer AAB+ students. Other institutions that have recruited to quota in the past also have had their control numbers cut and might have rejected applicants whom they would have accepted in earlier years.

The most important issue is that the reduction in total numbers in 2012-13 means that there must be many unfilled quota places. The government is proposing another core-and-margin exercise for 2013-14, and so it is very important to know whether those institutions that gained margin places have actually filled them. If not, there is little sense in further reducing quotas at institutions that could recruit more in order to give them to those that cannot - unless the motivation is actually to reduce the total number studying in UK ÖйúAƬ.

It would also be very informative to find out what has happened to those students who did not receive confirmed offers from their first- or second-choice institutions. We know that overall demand for places fell from 2011-12, but that was no surprise. However, it would be good to know whether applicants' behaviour has changed because they are now less likely to shop around in clearing. There are anecdotes, but firm data would be interesting.

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I suggest that the Universities and Colleges Admissions Service look at the destinations of students who were rejected at confirmation and compare them with similar groups in 2010-11 and 2011-12. Ucas could do this by looking at those rejected in August by a few of the universities that filled their quotas in the three years in question.

I volunteer my own institution for scrutiny, and perhaps a squeezed-middle Russell Group university might agree to join in, too.

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John Craven, Vice-chancellor, University of Portsmouth