Specifically because the paper is about house price, not rental price. For most people, the issue of achievable secure home ownership is different to rental affordability.
> multi-family housing units
Not really the kind of place that most people want to buy to live in for the remainder of their lives (unless starved of options).
> [multifamily housing units are] not really the kind of place that most people want to buy to live in
this is a descriptive norm - observed or perceived behaviors, preferences, and trends among a group of people who, typically, don't really have a choice to buy anything other than a detached house. Family-sized condos are actually highly sought after in dense urban areas where a detached house is an overt luxury, while in suburbs and rural areas they're a rare choice simply because it's illegal to build them.
I used to think this. Then I lived in an apartment for many years, and then I left. There's a big contingent of owner-occupiers in apartment buildings who don't stick around. It's just not a healthy way to live long term. I'm sure there are anecdotes from people who have stayed 5+ years full-time in an average apartment, and enjoyed it, and didn't yearn to be able to walk outside without being greeted by a (sometimes broken) elevator, or get a decent cross breeze of fresh air, or have access to sun all day long, but I'd wager they are the exception to the rule.
That is purely subjective. I would rather live in a condo in Manhattan than a single family home in Long Island.
I can see how this relates to housing affordability.
Would you rather live in the projects than a mansion in Bel Air?
A better comparison might be: would you rather live in a 4,000 sqft mcmansion in Santa Clarita or a modest 1200 sqft 3 bed 2 bath condo in Santa Monica?
What's that rhetorical question even relate to? Will increasing housing supply somehow make everyone more wealthy? The OP article claims not, and that's because that stock is going to rent-seeking investors, not buyers.
> A better comparison might be: would you rather live in a 4,000 sqft mcmansion in Santa Clarita or a modest 1200 sqft 3 bed 2 bath condo in Santa Monica?
Long Island vs condo in Manhattan wasn't really on even footing either.
This is such a true, yet sad, reflection of American society.
Doesn't everyone want to touch grass or have decent access to fresh air and sunlight? I guess if we could hypothetically build really cheap apartments deep underground, it would be sad if people didn't want to live there?