> In many areas there appear to be lots of empty living units
Citation needed.
(There is a problem with Prop 13 in California, where old people stay in houses that are way to big for them, removing supply from the marktet. But that's not the "empty apartments" you're referring to)
It all depends on the definition of empty. I take a practical approach: if there isn't someone sleeping in that unit regularly, it is empty. If I walk my dog through a neighborhood and see countless dark/cold apartments, ones where nobody has seen a light turn on in years and the mail either piles up or has been stopped, those are empty.
Others take different approaches. Some are of the view that a unit is not empty so long as it is listed as someone's "primary residence", irrespective of whether they actually sleep there.
Citation needed.
(There is a problem with Prop 13 in California, where old people stay in houses that are way to big for them, removing supply from the marktet. But that's not the "empty apartments" you're referring to)