Anecdotally, my apartment building has 0% vacancy rate. And a newer building across the street has at least 10 apartments vacant for the most of the year.

Anecdotally, i know quite a few boomers that own multiple properties (>3) in manhattan, some of which they rent some of which they keep vacant for when they want to come to the city I feel like at least some % of apartments in the city are visibly vacant most of the time because they are just part time homes for the wealthy.

The research for this does account for pied-à-terres, which do exist in some number but are a tiny fraction of he total and mainly exist in a handful of Manhattan neighborhoods. There are only about 10K of these in NYC[1] which is 0.27% of the 3,644,000 total housing units in the city. This just doesn't seem like a real problem when the rental vacancy rate is shockingly 1.4%[2] (of the 2,183,064 total rental units).

[1] https://www.brickunderground.com/buy/what-is-a-nyc-pied-a-te...

[2] https://www.nyc.gov/site/hpd/news/007-24/new-york-city-s-vac...

I struggle to believe that pied-a-terres are less than 1% in NYC, particularly in the post covid era. Maybe paid off condos in NYC owned by people who also live in Florida aren't counted somehow? Seems like everyone with a net worth of $2.5mm has two properties.

My best friend's brother has a rent controlled manhattan apartment that sits vacant 80% of the time and is used as a crash pad for a rotating cast of ~12 people, what do you call that?

Why would you struggle to believe something that is accounted for in tax records and other city records?

The median household income in NYC is about $70k almost no one relative to the population has a $2.5mm net worth. There are only 350,000 people in NYC with a net worth of more than 1mm.[1] Anecdote is clouding your understanding here, the idea that there are tons of empty units in NYC is just another luxury belief, it stands up to 0 scrutiny.

[1] https://finance.yahoo.com/news/n-y-c-more-millionaires-11000...

Or are corporate owned.

A good friend bought her Hell's Kithen flat (read: condo unit) from a Japanese company. Years ago I had another friend who worked for a company that had a sizeable place in the Village.

Anecdotal, but probably common enough.

There aren't that many. NYC housing data is sliced, diced, and studied by so many agencies, non-profits, think tanks, and so on that someone would notice. There's a marginal number of units that appear to largely unoccupied. Corporate and LLC ownership shows up in tax data and the totals are a drop in the bucket of the nearly 4 million units.

Yes, but you only need one unit per building to be over-bid and that then drives up the prices of other units in that building? It might not be an occupancy issue per se, but it doesn't help the overall residential market.

Housing exists in price bands more or less, so the thing you’re measuring has to be large enough to have an effect on the band. There’s a lot of research on NYC housing issues and no one has ever identified corporate housing as a contributing factor, so there’s a very high burden of proof on your claim.