I think the trick with compiling such a metric is defining it, and it's intended purpose. You've got one: compare the city of commoners to city of wealthy people. Or maybe a rich town locator.
With apartments, you get the sq. ft. of the dwelling, but there's also common areas. None of it being owned by the residents, merely rented. Contrast that with farm land, you'd have relatively few people with high amount of "owned land".
Sometimes very rich people choose to rent in ultra luxury apartments.
I wonder if part of the metric is something like, $ value of land / sq. ft. that is privately owned? Someone in Nebraska maybe owns 50 acres of land that is relatively low demand, versus say... a guy who owns a few golf courses in expensive areas.
The best advice you'll get! Always go to the source!
At worst, he gives you a cagey answer, and then you have information about how this person handles direct questions.
At best, he gives you an understandable answer and you grow closer as a result!
Generally speaking, think about forming your statements as "When you said/did X, I felt Y". This is sometimes called "telling your own story". Example...
"You were being evasive!"
Vs.
"When you went off the dating app, The story I made up about it is that you were trying to avoid me".
Even if it doesn't work out this is always great practice for life. Best of luck!