Jump in interest rates not just numbers on a spreadsheet

But it has also increased the pressure on the Reserve Bank Governor, Philip Lowe, who heads an institution crucial to the health of the economy yet known also for its feet of clay.

Monthly repayments on an $800,000 mortgage have now increased by around $780. That's a lot of spending power thrown to the wind.

These are not numbers on a spreadsheet, or coloured lines on a graph, but real people with finite incomes, household dependents, and rising costs.

If it hadn't already, the fourth upward ratchet in as many months, erased the rosy picture the RBA had voluntarily painted for borrowers.

The first hike in May was 25 basis points and the next three saw increases of an unusually steep 50 BP or half of one per cent each.

That's a savage correction from a situation said to be stable and under control. In the central banking business, credibility is everything.

Borrowers, whether in business or residential, are entitled to feel not just mystified, but betrayed.

"Given the outlook, the Board is not expecting to increase the cash rate for at least three years," Lowe had said when the cash rate was slashed to its lowest ever level of just 0.1 per cent, in November 2020.

Borrowers hadn't sought such certainty, nor expected it. But there it was - the official cash rate set at functional zero for years.

What was its purpose, this unusual certainty which enticed buyers to see their repayments as "affordable" for years to come?

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The technical answer is yield-curve control - a process where the bank had taken interest rates as low as they could go, leaving it with one last tool for signalling support for the pandemic-ravaged economy - the promise of "a reduction in the target for the yield on the three-year Australian Government bond to around 0.1 per cent".

The trouble was, markets decided that global circumstances had changed before the bank did and stopped taking this promise seriously. Hence the sudden reversal.

Prior to the pandemic, rates has been kept higher than many economists believe was necessary, putting downward pressure on pale economic growth and flat wages.

Now in 2022, it kept them low for too long, with the result that borrowers were lulled into a false sense of security, inflation stole a march, and the central bank is now playing catch-up. Once again the danger is of over-correcting.

Little wonder then that Treasurer Jim Chalmers has ordered the first review of the RBA in 30 years, with the three-member panel examining its 2-3 per cent inflation target, its structure and practices, and its deliberations.

Chalmers wants the report on his desk before he fills two board vacancies and before he has to decide on reappointing or replacing Dr Lowe.

Emergency settings didn't survive until 2024 and some believe Lowe won't either.