It has become a truism that GDP is a bad measure of prosperity and growth. But I never hear any good replacement suggested. I thought that perhaps total annual land rent can be an alternative measure, since it goes up with wealth, then I read Terence Michael Dwyer's book Taxation: The Lost History, and found out that he says the same, and more significantly, that Adam Smith has said largely the same:

"The land constitutes by far the greatest, the most important, and the most durable part of the wealth of every extensive country. It may surely be of some use, or, at least, it may give some satisfaction to the public, to have so decisive a proof of the increasing value of by far the greatest, the most important, and the most durable part of its wealth." - Wealth of Nations, Part 1, chapter 11

"Every increase in the real wealth of the society, every increase in the quantity of useful labour employed within it, tends indirectly to raise the real rent of land." - Wealth of Nations, Part 1, chapter 11

Quotes from Dwyer's book:

"The optimal policy is one that maximizes aggregate land rents, an echo of Adam Smith’s notion that the progress of society is a rent-maximizing process" (When discussing externalities as a cause of rents) - Terence Michael Dwyer, Taxation: The Lost History

"Smith’s economic goal for a nation was to maximize aggregate rent, in the absence of monopolies. This surplus or net product is truly the wealth Smith had in mind in the “wealth of nations.”" - Editor's summary of Taxation: The Lost History

Also discussed in the section 'Aggregate Rent as a Welfare Criterion'

I'm pretty confidant that this would be a good measure, and that, if land rent is taxed, the only way to increase land rents will be to increase prosperity. So whenever we hear someone complain about GDP being a bad measure, we should tell them about total annual land rents.

(note: land rent = land value = the potential excludable benefits generated by the unimproved portion of land)

What if we don't tax land? In that case it will be possible to increase rents in various ways that don't also increase prosperity. For example, anything that increases land speculation, like making capital investment more difficult, will lead to an increase in rent coinciding with decreased prosperity.

But there might be a way around that - extend the target from being just about maximizing aggregate rent, to also being about minimizing aggregate price. Under LVT the selling price of land becomes 0, so policy that raises land values would increase aggregate rent without increasing price. But if we look at the example above, where capital investment is made more difficult in the absence of LVT, though rents would increase due to increased speculation, prices will also increase. So if the metric we tried to optimize tracked both the maximization of rent and the minimization of price, it would not count that policy as positive.

Another reason Georgists should care about possible replacements to GDP is that, if we stop taxing productivity, we will also mostly stop tracking income, production and transactions, which, if I understand correctly, is required to calculate GDP. So shortly, a Georgist economy doesn't collect the information required to calculate GDP, so if it wants a measure of prosperity it needs something else, and total annual land rent is better, and is already being measured anyway, so it's the best option.