Students with places for the new academic term at St Norbert College near Green Bay, Wisconsin, could be forgiven for thinking that term has started early.

Most have already slept over on campus as part of a summer orientation programme. They have been required to register for classes and introduced to fellow students. They hear from the college at least once a week in the form of an email from an alumnus, a video from the president, a message from the college via Facebook, or an invitation to play a game of softball with campus employees or students.

But this is more than friendly midwestern hospitality. It is part of a concerted effort by US universities to meet the threat that students in financial difficulties will reconsider their decisions to enrol.

With the economy struggling and tuition fees increasing, throughout the summer institutions have been sweating over how many students will show up.

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There is even a term for this phenomenon: "melt". Fearing that many students will melt away, along with the tuition revenue they bring in, colleges such as St Norbert are working aggressively to stop that happening by contacting them regularly and bombarding them with gifts.

"Melt is always a concern," said Bridget O'Connor, vice-president for enrolment management at St Norbert, a small, private Catholic college in an industrial sector of the country that has been ravaged by the recession.

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"We're talking about it more this year than we have in the past because we want to make sure that those students who made the choice to come here are going to come, and that financial reasons are not a factor in them choosing not to attend," she said.

"We've had families whose circumstances have changed. Our message is that we're here to help."

The recession has prompted one in six university-bound students to change their plans, according to a survey by the College Board, a not-for-profit membership association with a mission to connect students with ÖйúAƬ, and the Art & Science Group, a ÖйúAƬ consultancy. One third said their parents' income had declined.

In a separate survey of admissions officials by the National Association of Independent Colleges and Universities (NAICU), nearly 40 per cent said the recession had already caused students to drop out. One quarter reported students switching from full-time to part-time study.

Almost 25 per cent predicted that the number of returning undergraduates would drop further, and 19 per cent said that some first-year students will not show up this autumn.

"What every admissions officer is saying is that this is the most unpredictable and volatile admissions season in memory," said Tony Pals, spokesman for NAICU.

In response, he said, "institutions have become more aggressive and innovative in reaching out to their accepted students. The name of the game this season has been engagement. The sooner you can make a student feel like part of the campus community, the less likely they are to decide not to enrol."

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This, Mr Pals said, appeared to be having the intended effect.

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"At every step in the admissions season this year, there have been dire predictions of looming disaster," he said. "You saw that back in the winter about how many applications would come in. Well, plenty of applications came in. You heard the same concern before deposits were due. And now you're hearing it with summer melt."

Tip of the iceberg

However, Rick Hesel, principal of the Art & Science Group, thinks the situation is more serious than universities are letting on.

"I don't trust what institutions are saying," he said. "Those that are having real problems - are they going to give honest answers? No way."

It will be at least another year before enrolment trends are known, Mr Hesel added. In the meantime, almost all the data he has seen suggest that the summer melt this year will be much higher than usual, especially at expensive institutions.

The Art & Science Group has found that students are opting for less expensive institutions - public instead of private and those offering two-year instead of four-year courses - along with those that offer more financial help and are close enough to home to allow them to commute.

Another survey, by the enrolment-management consultancy Maguire Associates, found that two thirds of families were basing university decisions on cost. But its chairman, John Maguire, a former admissions dean, said he was not convinced that the most grim predictions of summer melt will come true.

"There's certainly evidence that people are more concerned about their financial circumstances. I'd be surprised if that was not true," Dr Maguire said. But "education is such a high priority that we'll forgo our vacation or new car, but we're not going to forgo investing in our children's education".

However, the fact that universities are nervously checking the admissions data almost continually is an indication of how seriously they take the threat, he added.

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"A number of my clients are tracking things on a daily basis," Dr Maguire said.