> multiple non-residence ownership taxation One thing Copenhagen has done (in a not entirely coordinated way, with some messy parts) is to have large amounts o

> multiple non-residence ownership taxation One thing Copenhagen has done (in a not entirely coordinated way, with some messy parts) is to have large amounts of the housing stock just not permit non-resident ownership at all. A very common organizational structure is the resident-owned cooperative apartment building, and the bylaws usually require that you live there as your main residence as a condition of ownership: if you move, you sell. (Some exceptions for limited-time absences, e.g. if you take a sabbatical abroad, you can rent it in your absence without selling, usually for up to two years.) Another common organizational structure is buildings owned by nonprofit associations dedicated to building and maintaining good-quality housing. They rent but don't sell apartments; they do allow subletting but again with time limits. This particular class of buildings arose initially as "improve the housing of workers" type charitable initiatives (some funded by philanthropists, and some by labor unions), but the organizations have persisted to the modern era, and have continued to construct new buildings (partly through state support for construction costs). The market is being liberalized a bit lately, with many new buildings being sold as private condominium ownership. But there are some worries that if non-resident ownership is completely liberalized, the city will become like Paris, with a large proportion of apartments in the city center being pieds-à-terre owned by people who live elsewhere, which sit empty most of the year except when the owner wants to fly in to eat at Noma or something.