I think this whole article is predicated on an incomplete at best understanding of what “wealth” actually is. Money that goes into tax havens isnt converted into gold and stuffed in some underground swiss vault. It’s probably not even in the form of “money/currency” but more likely invested in real estate, companies, or other investment instruments. When a billionaire buys a company, the money leaves their bank acount and goes into the accounts of the company and is used for payroll, purchasing, research, etc… A billionaire can own 50% of a 2 billion dollar company and be said to have 1billion in wealth, yet have $0 in the bank. It makes very little sense for a wealthy person to have a lot of money in a bank, as it will not give them very good return on their investment, and as a result almost all the “wealth” of the 1% is out in the real world actively being used.
Some economists have suggested that in times of economic instability the wealthy will be more wary of risk and less likely to invest their money and that additional incentives should be used to encourage this. One suggestion is the idea of negative interest money, in which money loses value the longer you hold onto it. 100$ turns into $95 or even $50 if the same person keeps it for more than a year. Faced with the possibilty of half his money vanishing every year he keeps it, the billionaire is much more likely to buy a new car, renovate his house, invest in a business, or take a vacation in order to spend the money and reset the clock before the money vanishes. The downside of this is that it would be hard to design the system in such a way to keep track of who has own what for how long, and not also hit normal peoples savings.