A speculation and/or vacancy tax makes sense in cities with a high number of foreign buyers like Vancouver and New York but in other cities it seems like the biggest road block is simply zoning restrictions that prevent supply to meet demand. There are second order effects that need to go w/ more building, such as adequate transportation, parking and services. But if your goal is simply to get the average down can you do better than simply building more? Rent control seems more like a band-aid for a small number of folks rather than a real solution.