Fine, you could limit the tax to buildings identified as single and multi-family homes? Most of those 60% are not living in rental apartments. What it would do

Fine, you could limit the tax to buildings identified as single and multi-family homes? Most of those 60% are not living in rental apartments. What it would do is reduce the property value of existing real estate supply (by making expected cash flow from renting far less profitable), effectively forcing nonresident owners to sell their buildings to would-be renters, who would now be able to afford a mortgage on their homes. My thesis, fwiw, is that there's actually a sufficient supply of housing, it's just cornered with artificially inflated prices by people who treat housing as an investment vehicle rather than, well, housing.