Every teardown provides a clear picture of the land value for that neighborhood: the transaction price plus the cost of clearing off the old building. The similar sized lot next door is worth just as much. And the value of whatever improvement is on it is the difference between what the building-plus-land is currently worth, and the value of the land -- pretty much the depreciated value of the existing improvements.

Map these values, and you have a pretty good tool for good land assessments. And for lots a wider or narrower, or deeper or shallower, there have been very usable tables for over 100 years. NYC was doing this in the first decade of the 20th century.

A tax on land values asks us to pay to exclude others from our site. In the middle of nowhere, that price can be $0. On valuable sites, it can be quite high.

Today, a lot of city land is leased, and the tenant pays the landlord for the use of the land. The higgling of the market sets the price. There is a lot of revenue potential there, and collecting it for public purposes doesn't take from anyone something he created.

And that can't be said for sales taxes, or wage taxes, or taxes on buildings.