[somnic]

If I recall correctly, what's happening here is that a property is valued at a particular level based on the rent, and the owner can borrow against that to make other investments. Demand drops, and lower rents would affect the valuation of the property, the owner wouldn't be eligible to borrow as much against it any more and may not have the liquidity to readjust things. So it's more profitable and secure to keep the rents at a higher, but vacant, level. It kind of suggests the solution here is more regular and rigorous revaluations of property, or limits on how much it can be leveraged.