Manhattan https://www.theatlantic.com/ideas/archive/2020/01/american-h...
Seattle https://www.seattleweekly.com/news/luxury-apartments-whos-bu...
Melbourne https://www.theage.com.au/national/victoria/ghost-tower-warn...
Boston https://bostonagentmagazine.com/2018/09/11/study-bostons-new...
Vancouver: The article claims that there is ~5% vacancy rate. This is actually below the normal rate for vacancies in the US. Condos have a higher vacancy rate, but the article offers a reasonable explanation.
Manhattan: Ultra-luxury home vacancies aren't the same as luxury apartment buildings. Most people are not buying $5-$10 million condos. And even if the buildings are unsold, they aren't necessarily unoccupied.
Seattle: Again focuses on "foreign investors" and unsold apartments. No concrete data on how many those apartments are actually empty.
Melbourne: > Prosper Australia project director Karl Fitzgerald said, based on the water data, Melbourne's actual vacancy rate was closer to 7 per cent.
7% is on the high-end of vacancy rates, but if you reduced that down to 5% then the effect on prices would still be low.
Boston: No data on vacancy rates. Again, sale != occupancy. There are plenty of property management companies that build out luxury apartment buildings and directly rent to people.
The real issue is lack of housing, which can be fixed by letting developers build more housing, including high-end housing.
The Manhattan article links to https://www.nytimes.com/2020/01/10/realestate/new-york-decad... which says "Nearly half of new condo units in Manhattan that came to market after 2015... remain unsold, according to a December analysis of both closed sales and contracts" and "7,050 new condo units available for sale in Manhattan in January [2020]"
Melbourne: "Docklands... 17 per cent consuming no water in 2013" and "12.4 per cent of Cardinia and Clyde homes reported no water use."
Boston: "12 of Boston’s newest and biggest luxury developments could remain largely empty despite having sold most of their available condo units to buyers."
Manhattan: Unsold != unoccupied.
Melbourne: Now we're cherrypicking districts that have less than 15,000 residents total in a city of 5 million in one specific year? This is essentially p-hacking to support a non-existent narrative.
https://en.wikipedia.org/wiki/Cardinia,_Victoria
https://en.wikipedia.org/wiki/Clyde,_Victoria
https://en.wikipedia.org/wiki/Docklands,_Victoria
Boston: "could remain largely empty." This is speculation. Where is the data?
"Wealth investment leaves an estimated 125,000 homes in London without anyone living in them."
There are 268,385 empty homes in England according to the government (people get a tax break in most parts of England if they own a property that is unoccupied and unfurnished so its quite easy to track empty homes), and half of them are luxury houses in London.
I'm not saying that's definitely the case everywhere, but I am saying it's worth considering.
Also, the report doesn't tell us how many non-vacant homes there are in their survey area, so we have to guess. London reportedly has 3.59 million dwellings, so 25,000 vacant homes would only represent 0.7% of homes being vacant. Even if you use the higher 125,000 number, that's still only 3.5% of all homes. That's a fairly low vacancy rate, and about right for a city.
Even after the pandemic, housing officials report a 3.4% vacancy rate, which is the highest in eight years. https://lfpress.com/news/local-news/london-apartment-vacancy.... Before that, it was only at 1.8%. That's extremely low.
You can tax vacant homes, but in general, those taxes have a very small effect on housing prices. It's far, far more effective to allow people to build more housing, including luxury housing.
If the economy cannot consume all the products the suppliers produce you need to encourage consumption.
If you perfectly hit the balance (unlikely but in theory possible) then you need to do... nothing, neither savings nor consumption increases.
It depends on what your economy needs.