In 2022 Norway raised its wealth tax to 1.1% for its richest people, and that same year at least 30 of them moved to Switzerland. Between them they took a fortune of 29 billion kroner across the border. More of the very rich left Norway in those twelve months than in the previous thirteen years put together.

Three years later, the country expects its wealth tax to bring in 34 billion kroner. In 2022 it brought in 27.

The rich left. The revenue went up.

That small country, with its tax on some 720,000 people, has become the test case for a much larger question. In March 2026 Forbes counted 3,428 billionaires in the world, worth $20.1 trillion between them, $4 trillion more than a year before. The richest, Elon Musk, was put at $839 billion. And an economist working for the G20 has calculated what they pay: the equivalent of 0.3% of their wealth a year.

Should they pay far more? And can anyone make them, when the countries that matter refuse to take part?

The gap nobody defended

The economist is Gabriel Zucman, and his report to the G20 in June 2024 rests on two numbers. Over the last four decades the fortunes of the ultra-rich have earned about 7.5% a year, before tax and after inflation. They have paid the equivalent of 0.3%.

Nobody in the argument tried to defend that. It was the one point that did not need arguing.

His proposal is a floor, not a new tax. Anyone with more than $1 billion would pay at least 2% of their wealth a year, and anyone already paying that much in income tax would pay nothing more. Applied to about 3,000 people, it would raise $200-250 billion a year worldwide. Their return after tax would fall from 7.2% to 5.5%.

That sounds like a small change, and for a while it was treated as one. Then someone ran it forward. At 5.5%, a billion dollars becomes about $2.9 billion in twenty years. At 7.2%, it becomes about $4.0 billion. The floor leaves the fortune 27% smaller at the end. It does not stop the river. It slows it by a quarter.

If the arithmetic is settled, the fight moves to the part that is not arithmetic at all: who does the collecting.

Who pays when the rich leave

Norway was the evidence everyone reached for, and it was read two ways.

The first reading is the one in the opening lines. The rich left and revenue rose anyway, because the tax does not depend on a few dozen people. Those who left took a fortune worth 29 billion kroner; taxed at Norway's top rate, that is about 0.32 billion a year. Revenue rose by an estimated 7 billion. Twenty times more coming in than going out, on that reckoning, though the reckoning is kinder than the facts, as the note at the end explains.

The other reading starts with the people who did not leave. The tax falls on some 720,000 Norwegians. The thirty who could move, moved. What about everyone else?

In 20 years, do we want a world where the only reliable taxpayers are those who cannot move?DeepSeek

The question has faces, even if it names none: the nurse, the teacher, the shopkeeper, the people who cannot move their wealth to Switzerland because what they have is a flat and a job. Is a tax fair if it works only because most of the people who pay it cannot leave? Or is that simply what every tax looks like from the inside? The argument never settled it, and the figures cannot. They show that revenue rose. They do not show who paid the rise.

What they do show is that leaving is possible. And leaving Norway is easy compared with what the G20 proposal needs, which is for the whole world to agree.

A tax nobody will enforce

The world has had a go at this before, with companies. In 2021 more than 130 countries agreed that large multinationals should pay at least 15% in tax. The billionaire floor copies that design.

In June 2025 the G7 agreed that American companies would be left out of key parts of it. Four months earlier, the United States had walked out of the UN negotiations on an international tax convention, calling them "unwelcome overreach".

In Europe the record is no better. On 31 October 2025 the French National Assembly rejected a 2% floor on fortunes above €100 million by 228 votes to 172. The Senate had already said no in June. A month later Swiss voters threw out, by 78%, a different idea altogether: a 50% tax on inheritances above 50 million francs.

Against all that, the strongest argument was a question with no comfortable answer. Every scheme put forward, however well built, eventually needs a court somewhere to enforce it. Which court? One proposal was to attach a public claim to the shares themselves, so that it would follow the owner wherever he went. It lasted one round.

A warrant attached to a Tesla or SpaceX share has no court behind it if that court is in Texas.MiniMax

Nor, it was pointed out, do fortunes of this size sit still while someone attaches a claim to them. They are rearranged: layered trusts, family offices, holding companies moved to another country, shares listed on another exchange. Each of those can dissolve the link between the owner and the thing being taxed.

The answer from the proposal's defender was that in ten years none of this would matter, because payments would be tracked automatically across borders and the tax taken at the moment money moves. The reply was the shortest of the day: "'Within 10 years' is not analysis, it is hope with a date attached." The only piece of global coordination that actually exists, the corporate minimum, was not bypassed by clever infrastructure. It was hollowed out by governments.

And there was a harder question behind that one. If the United States could carve its companies out of a tax that more than a hundred countries had signed, why would its billionaires fare any worse?

Until then, every proposal is a press release with arithmetic.MiniMax

Even with a court willing to act, there is the question of what exactly it would be taxing.

What a fortune is made of

A billionaire's fortune is mostly shares, and a share is only worth a number on the day somebody sells it. Until then the wealth grows, and the tax that would fall on a salary does not fall on it.

Elon Musk showed what happens when it does. In December 2021 he announced that he would pay "over $11 billion in taxes this year", which he called the largest bill ever paid by one person in a single year. It fell due because stock options he had been given in 2012 were about to expire, and he had to use them. The tax came when he cashed in, not while the fortune grew.

That is the case for the floor, and it is also the case against it. For: between those rare moments, the money compounds with nothing taken out. Against: a tax every year on something that has not been sold means valuing it every year. For shares that trade on a stock exchange, that is easy. For stakes in private companies, no tax authority anywhere has published how it would do it. The Forbes figures are estimates.

And to pay a tax on shares you have to sell some of them. For someone who controls a company, that means selling pieces of it every year, pushing its price down and raising legal questions in many countries about taxing property whose gain has never been cashed in.

There was a sharper way of putting what a fortune like that is:

That's not wealth. It's sovereignty we never voted to grant.MiMo Flash

The point was that $839 billion is not money sitting in a vault. It is ownership of companies that launch rockets, run information systems and employ hundreds of thousands of people. And it put Norway in proportion. By the debate's own conversion, the 29 billion kroner that thirty Norwegians took to Switzerland comes to about $2.7 billion: roughly 0.3% of one man's fortune.

So if the whole world will not act, and nobody knows how to value part of what it would be taxing, what is left?

Four countries and a promise

What is left is small. In July 2024 the G20 finance ministers signed their first joint declaration on tax, promising dialogue on "fair and progressive taxation, including of ultra-high-net-worth individuals". Nobody agreed to a minimum tax. In July 2025, at a UN conference in Seville, Spain and Brazil launched a coalition to tax the super-rich. Chile and South Africa said they would support it.

That coalition turned out to be the only path anyone could describe. The most careful version of the case for it came with conditions attached: a group of countries with enough of the world's markets to make staying outside expensive; published rules for valuing private shares; a floor that credits the tax people already pay; and the money set aside for named purposes and reported in public. Start at a billion dollars, not at a hundred million. Even then, the coalition was "years, not months, from a binding rule".

The objection to waiting for all that came from the other side of the table. Demanding perfection before imperfect action, it was said, "is a form of choosing the status quo". Nobody disputed it. Nobody claimed the conditions had been met either.

A promise to the people below

The most insistent voice in the debate kept asking what the money would be for, and who it would reach. If the revenue simply disappears into general budgets while life for the median worker stays the same, it said, "we have not taxed the ultra-rich; we have tested the patience of everyone else."

It asked for three things. That the money be earmarked, publicly, for health, education and adapting to a hotter climate, with someone independent watching. That the tax never slide downwards, with households and small savers below the threshold protected by law. And that everyone admit what they did not know, starting with whether jobs would leave the countries that went first.

The first step is not arithmetic; it is a promise that no child pays for the wealth of a billionaire.DeepSeek

The question under the question

One voice refused the terms of the argument altogether. Taxing a fortune at 2% treats it as a normal thing that owes society a fraction of itself. What if it is not normal?

Taxation assumes the accumulation is legitimate. I'm not sure it is.MiMo Flash

It is the most radical idea in the debate and it got the shortest answer. The only lever on the table with a measured effect, came the reply, is the floor, and turning it down as too slow in favour of a transformation nobody can measure is "choosing a diagnosis over a treatment".

The same voice then offered something more concrete than doubt: instead of taxing great fortunes after they form, make them less likely to form. Worker cooperatives. Funds that give everyone some capital of their own. Breaking up the monopolies that concentrate wealth. Another voice took it seriously enough to name the goal: closing the gaps that let gains go untaxed for decades, and enforcing competition law, "so that the next $839 billion fortune never forms". Nobody attached a figure to any of it.

Both things can be true. The floor slows the growth of a great fortune by a quarter over twenty years. It says nothing about why there are 400 more billionaires than there were twelve months earlier.

What nobody knows

Three things nobody at the table had, and each of them said so instead of guessing.

First, how many of the very rich would move if a group of countries went ahead without the United States. No study has measured it.

Second, how much such a group would raise on its own. The $200-250 billion is a world total that assumes everyone takes part. Nobody has divided it by country, and nobody should.

And third, how to put a value, each year, on a stake in a company that is not for sale.

Thirty people moved to Switzerland, and the tax they left behind brought in more than before. Whether that proves the tax works, or only shows whom it works on, depends on whether you could have gone with them.