The empty properties are they owned or rented? If they are rented, are the tenants paying rent but just not using them? If they are owned, are the owners people

The empty properties are they owned or rented? If they are rented, are the tenants paying rent but just not using them? If they are owned, are the owners people who just used them for passive investment and don't rent them out? Otherwise I don't understand how rents can be so high? If there are places owned that aren't in use then the political solution seems pretty easy: tax property ownership massively when unused. Make unannounced visits to properties to see if the owners claim of having a property that's lived in is true.