You wouldn't run the regression on parcels of land only. You'd run the regression on parcels of land + improvements, run a PCA on the various attributes of both the land (acreage, viewshed, proximity to amenities, transit access) and the improvements (square footage, # BR/BAs, year of construction, presence of pool, presence of deck) to determine which factors materially affect valuation, and use the regression coefficients to subtract that out. So for example, you might find that going from 1BR->2BR costs an extra $200K, going from 2BR->3BR costs an extra $600K, a 9-rated school is an extra $500K, etc.

Now you take a sample of sales within the area of the parcel in question, subtract out the regressed values for the improvements, and smooth & average it, and you have a rough approximation for the value of the land. It's not going to be perfect: it assumes that features are linearly independent, for example. But it should be close enough, and doesn't suffer from the same incentive problems as letting a human assessor put in values for those features.

Here's a dumb idea:

- Take the most recent sale prices of all neighboring parcels within a quarter mile

- Take the land-area weighted average price per square foot

- Assess the given property as its land area times that average

Practically, this can be assessed without ever visiting any of the properties, and there are no games for either the assessors or the owners to play to manipulate it. Each neighbor serves as an example of the potential use (and therefore value) of local parcels. Yes, your hole-in-the-ground gets taxed the same as a skyscraper of the same size. Have you considered building something useful on it?

(Yes, as usual, parks, churches, and other non-economically-extractive community amenities would be exempt from _paying_ the tax, but that doesn't change the assessment)

Georgism actually massively decreases the cost of land, because the tax on land comes out of the future rental cash flows, and if set to equal the average rental opportunity cost of the parcel, washes them out to zero. You're left with only the structure value as the market price, which in many municipal areas is much lower.

In practice, it's likely going to incentivize large corporate landlords and tall residential towers near city centers (where this allows the greatest number of tenants to enjoy the natural amenities nearby), while pushing the poor and elderly out to the outskirts (where land is cheaper and structures are smaller). But that's probably what you want, since a larger number of income-generating residents can enjoy the inner-city amenities while the elderly have less use for them.

Simply put, because we want to incentivize people to build things that have not been built before, and by nature these are always monopolies when they get started. While with natural monopolies, no person built them, they were taken from nature, and so we don't want to incentivize people to profit simply from plundering what as there before. There's also a justice argument: most people are okay with people owning and profiting from work that they themselves did, but not okay with people profiting from taking control of the commons.

The idea of a "natural" monopoly is also fairly broadly applied in modern Georgism. Things like the natural resources, the electromagnetic spectrum, pollution, and greenhouse gas emissions are included, for example, in addition to land. There's a good argument for things like utility rights of way. Some proponents (more radical than I) also favor including IP in it, which actually would cover the google.com domain name.

I'd prefer some other mechanism (outside the scope of Georgism) to handle cases where "You built a monopoly through your own efforts to deliver a superior product, but now you've moved on and the current managers are mismanaging this resource to the detriment of society, but since it's a private monopoly there are no ways the get them to stop doing it." This is a really common problem in the economy today, and I'd like to find a way to manage it that preserves the incentive to invent new things while also removing the ability to prevent others from inventing new things.