[thuridas]

They can hide wealth (at their own risk) but it prevent them from extracting money from the country:

The cannot own houses, factories, monopolistic contracts o media. It makes harder to influence politics ( in a legal way).

The housing issue is specially important because city space is limited and the demand is very inelastic

[solidsnack9000]

I am not talking about hiding wealth. How do you find all of a person's wealth in a principled way? There isn't a central clearinghouse of this information.

People can own houses, factories, &c, in indirect ways, or in other jurisdictions, and these are all basically legal and make it hard to say what, exactly, people own.

The easiest people to tax are people whose inflows are simple wage income, who own a house and a car in their own country, and don't have a business. In other words, ordinary people. They make up a bulk of the financial activity in a country and the bulk of the tax revenues (most of the time).

It is easy to imagine that the way to capture greater tax revenue from wealthy people is simply to scale this system up -- tax the wealthy people more on their income, their expensive car, &c. However, wealthy people are also wealthy in structurally different ways from ordinary people.