Comment by tmnvix

Your links don't measure underutilised and vacant property (e.g. AirBnBs and second homes, or land banked properties).

From the links:

The homeowner vacancy rate is the proportion of the homeowner inventory that is vacant for sale.

The rental vacancy rate is the proportion of the rental inventory that is vacant for rent.

So essentially this is a measure of how many properties are vacant and available for rent or purchase.