The concept is simple and elegant on paper, but it's vulnerable to the same problem that real-world policies that philosophers come up with often fall prey to.

The concept is simple and elegant on paper, but it's vulnerable to the same problem that real-world policies that philosophers come up with often fall prey to. It's going to be incredibly difficult to assess the "unimproved value" of any parcel of land fairly. Do you apply a flat rate per acre of land regardless of where it is, to the detriment of rural farmers who own many acres? Or do you take the location into account? Are we going to have an army of certified professionals whose job is to assess the unimproved value of each and every parcel of land in the country? And if your formula makes any reference to the actual price at which land is traded, how do you tell how much of it is the unimproved value and how much of it is the value of all the improvements that went into it? There is hardly any land in populated parts of the world where no improvement has ever been made to it, so there's no reference point. If there are two parcels of land in the same neighborhood but one is more desirable because it has a view of the waterfront, does the waterfront view count as improvement or an intrinsic part of the value of the land? Everything is going to be based on a series of arbitrary decisions. Even the value of a dollar is based on a series of arbitrary decisions. Even worse, since it's all going to be an arbitrary benchmark with a lot of variables that can be tweaked, everyone will try to influence it or abuse it in a way that minimizes their own tax burden. Over time, these forces will result in lower assessments for all land, reducing the overall tax revenue and making the whole scheme unsustainable. Right now in the developed world, a disproportionately large share of people's wealth is tied up in real estate, especially for middle-class folks who read political philosophy. But this won't last if the incentive structure changes. I would much rather just bite the bullet and say yes, we're going to charge tax on the fruit of your labor whether Mr. Nozick likes it or not. Oh, and we're going to charge even higher rates on the fruit of non-human labor, i.e. machines, since they have no rights anyway. Maybe if these machines produce enough stuff, who knows, perhaps one day they'll contribute enough so that the tax on humans can be reduced to zero?