Variable-rate loans have lower initial rates than fixed-rate loans but can be more costly if interest rates rise.

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About half of mortgage borrowers have variable-rate loans and are therefore generally benefiting from the reduced cost of servicing their debt.

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Comparing variable-rate loans can be tricky because some private student lenders tie rates to the prime rate while others use the one-month or three-month London interbank offered rate, or Libor.

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The rise in variable-rate loans has been greatest in areas such as San Francisco, where house prices are highest, presumably because that is the only way that would-be buyers can afford to get their foot on the property ladder.

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Most helocs are variable-rate loans.

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Repaying debt has become more difficult in part because loan balances have grown and the interest rates on federal loans have increased as a result of a shift from variable-rate to fixed-rate loans.

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Delinquency rates on variable-interest-rate loans to subprime borrowers, which account for a bit less than 10 percent of all mortgages outstanding, have climbed sharply in recent months.

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Most Britons, for instance, still have variable-rate mortgages, although the proportion with fixed-rate home loans is rising (thanks, in part, to lower inflation).

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He found that the availability of discounted variable-rate deals crowded out comparatively expensive longer-term fixed-rate loans.

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