The second was pilots, who often ended up borrowing up to $120,000 over two years and tended to struggle to pay back the debt.
"They rack up large loans rather quickly and generally don't get the income to pay those off ... I've had a number of letters and emails from people who have got big loans from doing pilot training and really have just got themselves into a financial hole."
The third group was what Mr Joyce called "serial students" - people who study a ranges of things and continued to rack up a mounting pile of debt.
Mr Joyce said moves were under way to implement changes that would reduce the level of debt for both pilots and serial students.
Some of those changes included reducing the number of places available in pilot training and possibly capping the amount they can borrow in one year, along with preventing students from borrowing if they have an outstanding loan.
Mr Joyce said some of the borrowers with large loans would include those who are now living overseas and those who took out loans in the early days of the scheme but have not repaid their debt.
Nearly one million people have had a student loan since the scheme began, and four per cent of those who borrowed in the first year still have some outstanding balance. A further 12 per cent of original borrowers have made no progress towards any repayments.
Around 100,000 people have overdue loans which are worth $412 million. Of those, just over 50,000 are living overseas - some of whom have been the subject of a recent campaign to try to retrieve that money.
However, according to the report, the amount owed by overseas-based borrowers has actually increased by 27 per cent in the past year despite the campaign.
Mr Joyce said the pilot campaign, begun in October last year and targeting 1000 Australian-based borrowers, had been successful and has resulted in $8 million being repaid.
He said the campaign had cost $830,000 so "it's a return in an investment of about nearly10 to one, which is great".
Legal action is now being taken against a small group who haven't made any effort to start payments, and the programme is being expanded into the United Kingdom and further parts of Australia.
Mr Joyce said a number of other changes were being introduced to the loan scheme - such as restrictions on borrowing for older students and new residents - but would take years to flow through because it has had years of "build up of these historic debts".
Other highlights of the annual report include that 212,485 people had loans in 2010 - up 7 per cent from 2009. Of those, just over 63,500 borrowed for the first time, taking out an average of $7298.
In the year to June, $9.2 million was written off after loan holders died. A further $10.4 million was written off as a result of borrowers being declared bankrupt.
OUTSTANDING
$10,000 270,040 people
$10,000-$24,999 209,071 people
$25,000-$49,999 110,186 people
$50,000-$99,999 29,203 people
$100,000-$119,000 1,500 people
$119,999-$139,999 617 people
$139,999+ 541 people
TOTAL: 621,158
