More than 100,000 houses were empty in the latest census - and not just because their normal inhabitants were away.
But commentators say only a small portion of them are likely to be true 'ghost houses'.
In total, the census recorded 111,666 dwellings that were empty. Another 113,499 had their residents away when the Census was conducted. In 2018, 97,842 were empty.
Brad Olsen, chief executive at Infometrics, said houses could be empty for a number of reasons - including being a holiday home, being under renovation or having been recently constructed and not moved into yet.
He said, overall, 10.8 percent of total dwellings were unoccupied in the census, up from 10.2 percent in 2018 and 10.6 percent in 2013.
In 2013, only 2.5 percent were empty because their inhabitants were away. That increased to 5.5 percent in 2023.
Genuinely empty homes had gone from 8 percent in 2013 to 5.3 percent in 2023, he said.
"It's hard to know if they are 'ghost houses'," he said. "Given the amount of house building that has gone on in the last couple of years it's not impossible to think some of these are newly build and people haven't moved in yet.
"You can't say there are 100,000 homes that for some stupid reason are sitting empty while no one does anything with them. There will be various reasons, but I wouldn't say these are homes that no one would notice if you plonked a bunch of people to live in them."
He said it would be expensive at present, given high mortgage rates, for people to leave homes empty.
"If you weren't renting it out and getting some cashflow coming in, and you didn't own it outright, it would be a very expensive asset to have sitting there doing nothing."
He said it could be that more people were choosing to rent out their properties via Airbnb.
There was a particular increase in empty dwellings in Auckland, Gisborne and Hawke's Bay. Olsen said that was likely due to flood damage in Gisborne and Hawke's Bay, and a combination of flood damage and new building in Auckland.
Corelogic chief property economist Kelvin Davidson said Auckland only had about 4 percent of its housing stock sitting empty. Waikato had 8.8 percent, the West Coast and Marlborough more than 11 percent, and Northland about 10 percent.
"On the West Coast you wonder if there are older dwellings there that are a bit rundown. You drive around the West Coast and there are a bunch of houses where you think no one lives there - they might be counted as a dwelling but probably shouldn't be."
There seemed to be a strong 'holiday house' effect for areas such as Northland, and for Otago, where the 7.5 percent empty probably included a number of Queenstown properties, he said. Waikato's higher number would reflect Thames-Coromandel.
"At the other end you have Canterbury, Auckland, Wellington, Taranaki - there are holiday areas in those regions too, but they are the biggest regions population-wise, urban and not as renowned as holiday hotspots. It won't be the only factor, but it's one clear factor that does come to mind - the areas with relatively fewer empty houses don't tend to be thought of as a holiday destination."