"In 2014 (the most recent year with available data) there were about 387,000
housing units in SF. About 38% were owner-occupied, and the remaining 62%
or 240,000 were rental units."Very low property taxes should be relatively neutral between holding and trading compared to higher property taxes.
Prop. 13 encourages holding over trading because, while it does control property tax rate, it also constrains tax basis value increases to small annual increases while you hold property, but reassesses at full market value when you buy a new property. Which means, it increases the incentives to hold on to property once you've purchased it and decreases the incentives to purchase property, because the property is (net) higher value to the current owner than a new purchaser with otherwise similar profile, since the new purchaser would have to pay higher annual property taxes.