The index by analysts CoreLogic draws together a wide range of measures - including housing affordability, credit ratings, buyer demand, investor activity, and employment and population growth - to rate the vulnerability of every New Zealand region.
It doesn't predict coming downturns but rather estimates which regions are more vulnerable should a significant downturn hit.
Auckland is deemed more vulnerable partly because of its poorer credit rating.
It has more home owners paying interest only on their home loans rather than paying interest and the money owed on their mortgage, CoreLogic head of research Nick Goodall said.
This indicated there is likely more investors active in Auckland, he said.
But the question was whether there would be enough other buyers to step in and continue paying high prices for these properties, he said.
"That could play a part in the market plateauing or slowing," he said.
The analysis comes as the nationwide housing market now faces uncertainty and headwinds after prices jumped 28 per cent in the past year, fuelled by record-low interest rates.
Those skyrocketing prices have now led the Government and Reserve Bank to step in to try to engineer a slowdown to "sustainable levels" of price growth.
The Reserve Bank this month raised rates for the first time in seven years, while investors have been hit with new taxes, measures to make it tougher to get home loans and new tenancy rules favouring renters.
Added to that is uncertainty created by Auckland - and possibly other parts of New Zealand's - ongoing lockdown together with any unforeseen international headwinds, such as any potential blowout from the finance crunch in China's housing market.
Such uncertainty led CoreLogic to develop its latest vulnerability index, Goodall said.
It relies on six categories of data and gives each a weighting of how important they are.
They include housing affordability (25 per cent weighting), Centrix credit reporting (20 per cent), investor activity (15 per cent), demand/supply rebalance (15 per cent), StatsNZ local employment and economy data(15 per cent) and property demand data (10 per cent).
Using these CoreLogic found Christchurch is the least vulnerable to a significant downturn in part because its lower house prices make it much more affordable than other cities.
That, in turn, made it less likely owners would find that their home loan repayments have become so much of a burden they must sell, Goodall said.
The city also has fewer interest-only mortgages, more "restrained investor behaviour" and ongoing consistent demand from buyers, compared to Auckland where some buyer demand had dropped off during the recent lockdown, he said.
Among smaller centres Kawerau and Whakatane in the Bay of Plenty stood out.
Against neighbouring locations, Kawerau is rated among the most vulnerable towns and smaller cities, while Whakatane is among the least vulnerable.
That is due to Kawerau house prices shooting up phenomenally in recent years in a place where the population and numbers of new jobs had not grown enough to justify the prices, Goodall said.
Kawerau's job market has also recently been thrown into turmoil with the closure of the paper mill, the town's main employer, he said.
Nearby Whakatane, however, had a broad range of employment options - including from agriculture and forestry - and low credit issues, helping it to be rated among the least vulnerable towns.
Other areas to rank among the most vulnerable include a collection of towns in the Central North Island and tourist-hit MacKenzie, Queenstown-Lakes and Taupo where there has been a "slight uptick" in missed mortgage repayments, Goodall said.
The upper South Island and Canterbury regions look less vulnerable than most of the rest of the country, however.
"It's also important to note the areas expected to underperform may not necessarily see values fall, but in relative terms they face the greatest economic risks, which makes them more vulnerable to a downturn," Goodall said.
