I don't follow that. Suppose the tax was 100%. Real estate would effectively never appreciate, so no one would hoard it. If the tax is 0%, then it's a completel

I don't follow that. Suppose the tax was 100%. Real estate would effectively never appreciate, so no one would hoard it. If the tax is 0%, then it's a completely "free" market. Anything between the two just reduces the ROI. Since a high ROI in the short term promotes speculation (and not development), it seems like this would reduce speculation and the likelihood of bubbles forming. Of course that's a ridiculously oversimplified view. There are a zillion different ways to stack this, which is what would happen in any case. To spur development and not just buy-and-hold, the law might be written to exempt certain kinds of improvement costs.