The bank put out a report showing that, over the past 30 years, variable-rate mortgages have been more cost-effective about 82 per cent of the time.

That may come as a surprise to some after studies have shown many Canadians prefer a fixed-rate mortgage.

A fixed rate locks the borrower into a set interest rate for a certain period of time.

That gives many borrowers peace of mind knowing how much money to set aside each month for their mortgage payment.

Variable rates change along with interest-rate moves.

BMO said the Bank of Canada's overnight lending rate is at its lowest possible point now, which could mean there are fewer benefits to a variable rate in the foreseeable future.

BMO highlighted two historical periods when fixed rates were considered beneficial - in the late 1970s and late 1980s - and both were just before interest rates started rising again.

The bank added that the current interest environment is similar to both of these periods.

Canada has been in a long-term declining rate environment since the early 1980s, the bank suggested.

As a result, the spread between five-year fixed mortgages and variable mortgages has been pushed wider in recent years, and is now near an all-time high.