In order to reduce speculation in its housing market, the city of Vancouver imposed a vacant property tax. People would be assessed an additional tax if a house or apartment was left vacant for a long period of time. (Yes, this is one of my pet ideas, so it makes my day to see Vancouver moving ahead with the vacancy tax.)
In addition to reducing speculation it might be expected that the tax would reduce rents by making more units available. But CBC says it ain't so, there will be more supply but no change in prices. Interesting how things work up north.