Why a Substantive Wealth Tax Cannot Work: The Liquidity Problem Nobody Designs Around
The aim behind a wealth tax is not hard to understand, and it deserves to be taken seriously rather than dismissed. The argument that those who hold the most should contribute more, and that extreme concentrations of wealth sit uneasily alongside strained public services, is a fair position for people to hold. Nobody serious should pretend the underlying concern is illegitimate.
The problem is not the aim. It's the mechanism. A wealth tax, applied at any rate substantial enough to matter, runs directly into a structural fact about how the wealth in question actually exists — and that fact doesn't bend to political will, however well-intentioned the policy behind it.
The Number on Paper Is Not the Number in the Bank
Take Elon Musk's holding in SpaceX as a concrete illustration, using the actual current numbers rather than a hypothetical. SpaceX listed on Nasdaq in June 2026 following its merger with xAI, pricing its IPO at $135 a share in the largest public offering in history. As of mid-2026 the company's market capitalisation sits close to $2 trillion, and Musk's personal stake is roughly 42% of the equity — something in the region of 6.4 billion shares.
Multiply his share count by the trading price and you get a headline "net worth" figure in the hundreds of billions. That figure is real in one specific, narrow sense: it accurately reflects what his shares are worth at the current market price, for the volume of shares that actually trade. It is not real in the sense that matters for a tax bill. It is not cash. It has never been cash. And there is no mechanism by which the government, or Musk himself, can convert a meaningful fraction of it into cash without changing the number it was supposedly measuring.
Why the Starting Number Is Already an Illusion
Before we even reach the question of what happens when shares are sold, there is a more basic problem with the valuation itself. The $125 share price is not a measure of what SpaceX is worth in any absolute sense. It is a measure of what supply and demand will support for the 500 million shares that currently trade — the public float. Multiply that price by the 13 billion shares that exist, and you produce a headline market capitalisation figure that looks authoritative. But the mathematics is invalid from the start.
[This is where the structural illusion begins — and it is not unique to SpaceX. The $125 share price is set by supply and demand for the 500 million shares that actually trade. The remaining 12.5 billion shares are locked up: Musk's stake, institutional holdings, restricted stock. Multiply the float price by the full outstanding share count and you produce a headline valuation that looks authoritative, but the number is a mathematical projection, not a realisable sum. Every listed company operates this way. The float is always smaller than the outstanding shares. The headline market cap — the very figure a wealth tax would use to calculate liability — is always an overstatement, because it assumes the full share count can be liquidated at the current marginal price. It cannot. The price depends on the stock not being sold. A wealth tax that levies a charge against this headline number is not taxing wealth — it is taxing a modelling assumption. And the moment it forces a sale to collect, the assumption collapses.]
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The price per share exists because 12.5 billion shares don't trade. The scarcity of available shares is what supports the price. To then take that scarcity-derived price and apply it to the very shares whose absence created it is not a valuation — it's a category error dressed up as arithmetic. If you attempted to introduce those 12.5 billion shares into the market, you would not receive $125 for each of them. You would receive a rapidly declining price as supply overwhelmed demand, and the final figure would be a fraction of the headline number. The wealth being taxed never existed in the form the tax calculation assumes. It is a mathematical ghost — a theoretical, illusory vanity figure produced by multiplying a flow price by a stock quantity, without accounting for the fact that the price depends on the stock not being sold.
This is not merely a SpaceX problem. Every listed company has a float that is smaller than its outstanding shares. The headline market capitalisation — the number that would be used to calculate a wealth tax liability — is always a projection that assumes the full share count could be liquidated at the current marginal price. It cannot. The float is what trades. The rest is locked up: founders' stakes, institutional holdings, restricted stock, unexercised options. The price you see on the screen is the price for the shares actually available. Apply it to the shares that aren't, and you are no longer doing finance — you are doing astrology with a spreadsheet.
This is the structural absurdity at the heart of any wealth tax applied to equity holdings. It levies a charge against a number that can only exist under conditions the tax itself makes impossible to maintain. The valuation is real only so long as nobody is forced to test it — and the tax, by design, forces the test.
Why the Price Cannot Survive the Sale
A share price is not a fixed, stable fact about a company. It is the outcome of supply and demand meeting at a specific volume, at a specific moment. SpaceX's current price reflects what buyers are willing to pay for the shares actually available to trade — the public float, plus whatever locked shares gradually unwind over time. Musk's entire 6.4 billion share stake sits under an extended lockup that doesn't expire until June 2027, specifically because the market cannot absorb that volume of supply without the price collapsing under the weight of it.
This is not a technicality. It is the entire point. If a wealth tax required Musk to liquidate even a modest fraction of his stake in a single tax year — enough to raise a meaningful sum against a bill calculated on a headline valuation in the hundreds of billions — that sale would itself have to be disclosed. As a company insider and affiliate, any sale of that scale would require an SEC Form 4 filing, and any regular disposal programme would typically run through a Rule 144 volume-limited, pre-scheduled 10b5-1 plan precisely because dumping a large block onto the market at once moves the price against the seller. The market would see the filing, correctly interpret it as forced or semi-forced selling from the largest holder, and price the stock down in anticipation of more to come. The $2 trillion valuation the tax bill was calculated against would not survive contact with the sale required to pay it.
This produces an almost absurd loop: the tax is levied against a number, the payment of the tax destroys the number, and the following year's tax bill is calculated against a lower number that was only lower because of the tax. Chase that far enough and either the tax raises steadily less than projected, or it functionally forces a controlling founder to surrender control of the company entirely, share sale by share sale, to pay tax on a valuation that existed only because he hadn't yet been forced to sell.
This Is Not Just a Problem for Billionaires
Wealth taxes are aimed at extreme wealth, and it's fair to note that most people will never be personally affected by one. But the underlying mechanical problem — taxing the estimated value of an illiquid asset rather than actual income — is exactly the same one that shows up, at smaller scale, in ordinary council tax and any proposed property-based wealth levy. If you owned your home outright and were taxed annually not on income but on the assessed market value of the house and the car on the drive, you would face the identical structural bind: the asset is worth something on paper, but nothing about that valuation puts money in your account to pay the bill. Your options become selling the asset, borrowing against it, or falling into arrears — none of which is what "the rich should pay more" was supposed to produce for a pensioner sitting in a house that happened to appreciate.
What Forced Selling Does to the Market Being Taxed
Scale the SpaceX example up to a genuine, economy-wide wealth tax and the same mechanism compounds. If a meaningful number of large holders are simultaneously required to liquidate portions of equity, property, or other illiquid holdings to meet the same annual tax deadline, that isn't isolated selling — it's correlated selling, concentrated in a predictable window, which is precisely the condition that moves prices hardest. Equity markets would see recurring, forecastable downward pressure timed to tax season. Housing markets subject to a similar logic would see exactly what you'd expect from a wave of reluctant, tax-driven sellers meeting buyers who know the sellers are under time pressure: falling prices, precisely among the class of asset the tax was trying to capture value from. Since the tax is calculated as a percentage of assessed value, a falling asset base directly shrinks the revenue the tax was designed to raise — the policy would be undermining its own tax base in real time.
The effects don't stop at the specific asset class. Forced liquidation at scale to raise cash tends to spill into the safest, most liquid instruments available — government bonds being sold to raise cash quickly, or foreign holdings being repatriated or converted, put pressure on bond yields and currency markets that have nothing directly to do with the wealth tax's stated target. A policy aimed narrowly at billionaires' equity stakes can end up moving the cost of government borrowing and the exchange rate for everyone, simply through the mechanics of large, correlated, time-pressured selling finding its way into adjacent markets.
The Incentive Problem Underneath the Mechanics
There's a second-order effect worth naming directly: who continues to build, or invest early in, a company under a tax regime that forces them to sell down their own ownership stake every year simply to remain compliant, regardless of whether the company has generated any cash they could actually use to pay it? Founder-controlled companies exist because control was worth retaining through years of no profit, in exchange for equity that might eventually be worth something. A tax that forces annual dilution of that control, independent of any liquidity event, changes the calculation for anyone deciding whether founding or scaling a company in that jurisdiction is worth doing at all.
Why "Switzerland Manages It" Isn't the Counterexample It Looks Like
Switzerland, Norway, and Spain are usually cited as the proof that a wealth tax can be made to work, and Switzerland's is often held up as the durable, successful version. Look closer and the example undermines the point it's meant to support. Switzerland's wealth tax is a cantonal patchwork, with several cantons offering low headline rates and lump-sum taxation deals specifically designed to attract wealthy foreign residents. It functions, in practice, as the destination wealth flees to — not evidence that a wealth tax survives contact with mobile capital, but a live demonstration of where that capital goes once it starts moving.
Norway supplies the data. After the government raised its wealth tax rate by just 0.1 percentage points in 2022, 82 Norwegian billionaires and multimillionaires left the country across 2022 and 2023 — more than had left in the previous thirteen years combined — taking roughly 46 billion kroner (around $4.3 billion) in wealth with them. More than 70 of them moved specifically to Switzerland. Fishing-and-industrial magnate Kjell Inge Røkke, at the time Norway's third-richest person, said plainly on departure: "My capital will continue working in Norway" — the tax hadn't captured the wealth, it had simply relocated the person attached to it, at a cost the Norwegian treasury is still absorbing in lost annual revenue.
France offers an older version of the same pattern, wrapped in a widely repeated but genuinely contested statistic: London has long been called "the sixth biggest French city," a line used by Boris Johnson and reported in French media since the Sarkozy era. British demographic data disputes the precise ranking — official population figures put the real number of French nationals in London well below what would be needed to support that claim literally. But the underlying migration is real and well documented regardless of the exact statistic: France's wealth tax and François Hollande's 75% top income tax rate drove a genuine, sustained wave of wealthy French residents, from Gérard Depardieu to a long list of bankers and entrepreneurs, into London specifically. France repealed its wealth tax in 2018 in significant part because of exactly this dynamic.
The pattern is currently repeating in the UK itself. Following Labour's October 2025 budget and its changes to capital gains and inheritance tax treatment, wealthy residents have been leaving Britain for lower-tax jurisdictions — property investors Ian and Richard Livingstone relocated their residency to Monaco in early 2026, one of a wider group of departures reported through 2026. France's own finance ministry has since expressed concern about a wealth-tax "race to the bottom," worried that any further increase on their side will simply accelerate flight toward the UK's more favourable regime — the same dynamic in reverse, showing this isn't a France-specific or Norway-specific quirk. It is what mobile wealth does whenever one jurisdiction's tax burden diverges meaningfully from a nearby alternative's.
Where the Fair Counterargument Actually Sits
None of this means the underlying concern about concentrated wealth is illegitimate, and it's worth being precise about where genuine, defensible disagreement still exists rather than treating the case above as fully closed.
Some proposals are explicitly designed around the liquidity and mobility problems rather than ignoring them. Senator Ron Wyden's billionaires income tax proposal in the US treats unrealised gains as pre-payment against eventual realised gains, with multi-year payment and deferral provisions for genuinely illiquid holdings. Property-based wealth taxes have one genuine structural advantage over equity-based ones: real estate cannot relocate to Switzerland the way a person or a share portfolio can, which removes the mobility escape route, even though the forced-sale price-impact problem described earlier still applies in full. And a wealth tax coordinated across multiple major jurisdictions simultaneously, rather than imposed unilaterally by one country, would close off much of the "just move to the country next door" option that the Norway and UK examples above depend on — genuinely difficult to coordinate in practice, but not a logical impossibility.
What the evidence above does establish fair
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Trading Beyond Charts
ly firmly is that a wealth tax imposed by a single jurisdiction, on mobile capital, without serious accommodation for both the liquidity problem and the migration incentive, will lose a meaningful share of its intended tax base to relocation before it ever collects the revenue it was modelled on. Whether a more careful, internationally coordinated, immobile-asset-focused design could avoid both problems at once is the genuine open question — and it's a much harder design problem than "tax the billionaires" makes it sound.