Do you think that's a problem with existing property taxes?

The main difference between property and land tax is that with a land tax, the structure isn't taxed. So you can build up "for free" wrt taxes, which encourages more density on the most valuable land.

E.g. land in the middle of downtown San Francisco that's currently rented out as a flat parking lot, could instead be built up into multi level parking or housing instead. Whereas the current tax structure would punish such developments by increasing the tax (which is why it's still a flat parking lot).

San Francisco is an interesting case cause they used to have a land tax and economists argued that's what cause San Fran to be quickly rebuilt after it was burned to the ground in 1906. Land owners were still taxed the same, even though their building was gone. They'd have to either sell or rebuild.

Contrast that with New Orleans after Hurricane Katrina. Property owners had their buildings destroyed, so taxes went to zero (taxes based on the property value, not the land value). This incentivized property owners to wait and see if their neighbors would rebuild rather than take immediate action.

> San Francisco is an interesting case cause they used to have a land tax

Property taxes on land aren't unique to San Francisco. It's basically standard practice in most cities to have one tax for property and one tax for improvements.

> Contrast that with New Orleans after Hurricane Katrina. Property owners had their buildings destroyed, so taxes went to zero (taxes based on the property value, not the land value)

New Orleans has separate property taxes on land and structures, so property taxes did not go to $0 after Katrina.

Overall property tax rates went up because income from taxes on structures went down, but unimproved lots still get a tax bill.

Are there any places outside of PA that do this in modern times?

That's works only if you're an investor. You're going to rebuild your home immediately, finance optimizations be damned.

But that's not what happened. People didn't rebuild their homes, they left and never came back.

As a consequence of the tax, or because of the risk of rebuilding in a flood zone?

Most serious study on this suggests it would have the opposite effect: make it harder for the wealthy to horde land in the form of low density residences in prime locations where townhomes and apartments would be a much better economic outcome enabling many more people to live affordably in close proximity to their jobs.

I don't buy that. If there's one party benefitting from such tax, it's big players who can afford tighter margins. It's a play that mostly favours monopolists, who can also afford to have "serious studies" made.