Today's Reserve Bank decision on the Official Cash Rate is almost certain to be historic.

The central bank is expected to raise the OCR by 75 basis points today, the highest rates hike ever.

That would bring the rate to 4.25 percent, it's highest point in 14 years.

ANZ Chief Economist Sharon Zollner told Mike Hosking there's a small chance they will go even further, and raise the OCR by truly unprecedented one-percent, to 4.5 percent.

The OCR is now expected to peak above five-percent.

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