Don't have sources offhand but my recollection is that vacancy taxes have also been tried before and, while they do have some effect, the vacancy rates in most

Don't have sources offhand but my recollection is that vacancy taxes have also been tried before and, while they do have some effect, the vacancy rates in most locales with high costs of living are already low enough that it doesn't help that much. Vacancy rate statistics include things that are pretty natural and you wouldn't really want to penalize, like an apartment being briefly vacant after the previous tenant moves out and before the next tenant moves in. So you can't just look at the rental vacancy rate in a city being (say) 3% and conclude that those 3% of units in the city are being held vacant and off-market. There may be some of those, but it's a far lower percentage. Which is to say, institute a vacancy tax if you like (it won't really hurt if done sanely), but realize that it won't be a silver bullet here.