The Bank of Canada has raised its key interest rate by a bigger than expected full per cent to 2.5 per cent. Analysts had expected an increase of three-quarters of a point. The biggest rate increase since 1998 is going to put a lot of homeowners with variable rate mortgages into a cash-crunch situation, as the big banks are sure to raise their rates in response. The central bank is boosting the rate aggressively to try to tackle soaring inflation.