Ignoring a “car park full” sign requires nerves of steel and a large helping of blind faith.

On rocking up in the Mazda to find the “Full” sandwich board plonked at the entrance of the North Terrace car park on Thursday morning, I had mere seconds to make a decision before being honked by fellow motorists.

The car park serves the western end of the Convention Centre – scene of this year’s ritual State Budget media lock-up.

Ignoring the “permit holders only” warning, I headed into the carpark’s constipated concrete bowels. And there, just three car spaces in from the entrance, was a vacant space. Winner, winner, chicken dinner. The driver behind me, also not a permit holder, nabbed a space only another five cars away.

A name exists for this devil-may-care approach to warning signs. It’s called “confirmation bias”, defined as “the tendency to search for, interpret, favour, and recall information in a way that confirms or supports one’s prior beliefs or values”.

“People display this bias when they select information that supports their views, ignoring contrary information, or when they interpret ambiguous evidence as supporting their existing attitudes,” Wikipedia explains. “The effect is strongest for desired outcomes, for emotionally-charged issues, and for deeply entrenched beliefs.”

I have a “deeply entrenched belief” that carparks are never as chockers as they claim to be.

And anyone who has kept an eye on all recent South Australian budgets, mostly Labor and the one-term Marshall Liberal efforts, should by now have a deeply entrenched belief that our Treasurers suffer from confirmation bias.

The 2023-24 Budget papers are stapled together with some heroic assumptions about the future of the national economy, interest rates, debt, and the capacity to return to a $250 million operating surplus in the 2023-24 Budget.

Photo: Brett Hartwig/InDaily

The government knows the financial risks built brick-by-brick into this year’s Budget papers, but it is choosing to believe that it can deliver on all its fiscal targets, despite strong evidence over at least the past two decades that it almost certainly cannot and will not.

A state budget with spending nudging $25 billion, no attempt to control public service job numbers, debt ballooning 50 per cent to more than $37 billion within the next four years, and a predicted operating surplus of $233 million that somehow became a $240 million deficit this year – a $500 million whoopsie  – isn’t a full car park, it’s a car crash waiting to happen.

Unless all the jagged pieces fall into place, and they rarely do.

The 2023-24 Budget papers are stapled together with some heroic assumptions about the future of the national economy, interest rates, debt, and the capacity to return to a $250 million operating surplus

But the government has tied its own hands. It is sticking to last year’s election promise of no new taxes and no increased taxes and it is throwing bucketloads of cash at the hospital system because it knows it has to shake off its “Labor will fix ramping” hoodoo before the next election in 2026.

Treading a well-worn path, most of the positive news from this year’s budget, and the bad news on the deficit, has already been strategically rolled out over the past fortnight.

The welcome surprise from the lock-up is the abolition of stamp duty for eligible first home buyers purchasing or building a new home.

While Labor Treasurer Kevin Foley liked decorating his budget papers in his beloved Port Power colors of teal, black and white, the dominant image in Treasurer Stephen Mullighan’s work this year is of a young man and woman happily loved up at the front door of their own home.

It stayed up on the big screen throughout the four hour lock-up, just in case we didn’t get the message.

“This budget represents what’s on the front cover,” he said of the image of a traditional heterosexual couple presumably at the door of their home completed by a builder who hopefully hasn’t gone bust.

But three key figures in the budget papers reveal the bills racked up that will have to be serviced by present and future generations, including the children and maybe the grandchildren of those happy, home-buying couples.

Last year’s budget forecast state debt would be $16.9 billion by now. The actual figure will be $24 billion. By the end of the Budget’s forward estimates in 2026-27, debt will be $37.5 billion.

Treasurer Stephen Mullighan says this 50 per cent increase is sustainable thanks to a buoyant jobs market, increased revenues from the untamed real estate market and increased GST revenue.

It takes the state’s net debt to revenue ratio from 100.5 per cent to 121.6 per cent. This is a critical figure, because it represents the shortfall in revenue to service state debt.

The Treasurer’s argument that it is lower than the debt to revenue forecasts of the last Marshall Liberal Budget is cold comfort for those who worry about how we service debt.

Former Liberal Treasurer Rob Lucas happily racked up debt when the state government could borrow cash at a little over one per cent.

Rising world interest rates have shredded that bargain. Interest expenses are starting to bite sharply for the state, rising from $505 million in 2021-22 to $780 million in the current year. They are forecast to hit an eye-watering $1.68 billion by 2026-27.

When I buttonholed the Treasurer to ask if he was worried by the rise in debt his answer was an unequivocal “yes”.

But he said his real concern wasn’t the bald debt figure, but the rising cost of servicing the debt. While debt would leap by 50 per cent, the debt payments would triple.

“The reason we try to arrive at our budget surplus, and a healthy one, is so you can stomach those rising interest costs,” he said.

When asked at the media conference about his forecast of future rate hikes, he said that “predicting what’s happening to interest rates is a mug’s game” but he hoped the rises were over.

If only we all could have a deeply entrenched belief that he’s right.

Matthew Abraham is InDaily’s political columnist. Matthew can be found on Twitter as @kevcorduroy. It’s a long story.