Why the California Prop 40 billionaire tax turned into a fight over who gets to leave

Six billionaires packed up and moved before New Year's Day, and their departure tells you almost everything you need to know about the measure now sitting on California's November ballot. Larry Page, Sergey Brin, Peter Thiel, Travis Kalanick, Don Hankey, and Steven Spielberg were reported to have relocated to Miami, Las Vegas, Texas, and New York ahead of a January 1, 2026 residency cutoff written directly into Proposition 40. That cutoff was not an accident. The people who drafted this tax knew the wealthy would try to run, so they set a date and dared them to beat it. Roughly six of them did.

This is an opinion column, and my opinion is straightforward: the fight over the California Prop 40 billionaire tax has become less a debate about tax policy than a referendum on whether a handful of extraordinarily mobile people should get to decide how California funds its hospitals and schools. I think the answer voters give in November matters far beyond this one state, and I think both sides have been less than honest about what the measure will actually do.

What Proposition 40 actually asks California voters to approve

Let us start with the text rather than the talking points. Proposition 40, formally the 2026 Billionaire Tax Act, qualified for the November 3, 2026 general election ballot after the Secretary of State certified more than 980,000 valid signatures on June 17, 2026. It imposes a one time 5% tax on the net worth of individuals and trusts holding more than $1 billion in what the measure calls covered assets: businesses, securities, art, collectibles, and intellectual property. It pointedly excludes directly owned real estate, which is a meaningful carve out, and it fixes tax residency as of January 1, 2026.

The 5% is not collected in a single hit. It is payable over five annual installments of 1% each, starting in 2027 and running through 2031. Proponents, led by the labor union SEIU United Healthcare Workers West and drafted with input from UC Berkeley economist Emmanuel Saez and law professors Brian Galle, David Gamage, and Darien Shanske, project the levy would raise roughly $100 billion over those five years from something like 200 to 214 of the state's wealthiest residents.

Read that number again. A hundred billion dollars from around two hundred people. Whatever you think of the policy, the concentration of wealth it implies is the actual story here, and it is the reason the California Prop 40 billionaire tax has drawn national attention rather than the shrug that greets most state ballot measures.

California Prop 40 billionaire tax

The drafters were not naive about flight. A wealth tax with no residency anchor is an invitation to change your driver's license and keep your money. So they anchored residency to January 1, 2026, meaning your liability was supposed to be locked in before most voters had even heard of the measure. The theory was elegant: by the time billionaires realized what was coming, the door would already be shut.

The problem is that some of them saw it coming anyway. According to Fortune's March 17, 2026 analysis, the six billionaires who relocated before the cutoff would alone have generated an estimated $27 billion of the projected $100 billion. That is more than a quarter of the entire revenue projection walking out the door before a single vote was cast. If that ratio holds, or worse, if it accelerates, the fiscal case for Proposition 40 starts to wobble under its own optimism.

I want to be fair to the proponents here, because the exodus argument gets deployed lazily. A one time tax, by design, is harder to flee than an annual one: you cannot escape a levy that has already attached to you on a date in the past. The whole point of the January 1 anchor was to make leaving in 2026 or 2027 pointless. Whether the courts agree that California can tax someone who was a resident on that date but has since left is a separate and genuinely unsettled question, and it is exactly the kind of ambiguity that funds a decade of litigation.

Sergey Brin's counter ballot machine

If you want to measure how seriously the wealthy take this, look at what they are spending to stop it. Sergey Brin, whose net worth Forbes estimates at around $300 billion, co-founded an opposition group called Building a Better California with Eric Schmidt. Brin has reportedly contributed roughly $82 million to fund two countermeasures, Proposition 41 and Proposition 42, designed to weaken or outright invalidate Proposition 40 if it passes.

Think about the logic of that spending. Eighty two million dollars is a rounding error against a $300 billion fortune, but it is an enormous sum in the context of a ballot campaign. It is also a rational bet: if Proposition 40 would cost a billionaire even a few billion dollars, spending tens of millions to kill it is one of the highest return investments available. This is the part of the debate that voters should sit with. The measure is a test of whether concentrated wealth can simply buy its way out of a democratic decision, and the counter ballot strategy is that buyout in its most literal form.

I do not say that to demonize Brin, who is entitled to oppose a tax he considers confiscatory. I say it because the existence of Propositions 41 and 42 changes what a Yes vote on 40 even means. Voters may approve the tax and still watch it dismantled by measures on the same ballot, which is a genuinely confusing thing to ask of an electorate.

Gavin Newsom's break with his party's base

The most politically interesting fact in this whole affair is that the tax's loudest opponent is a Democratic governor with national ambitions. Gavin Newsom told Politico the plan "makes no sense" and is "really damaging to the state," warning it could trigger exactly the billionaire exodus that Fortune's numbers hint at. He is not alone among the state's leadership. Both leading candidates to succeed him, Democrat Xavier Becerra and Republican Steve Hilton, oppose the measure as well.

Newsom's opposition is a tell. Here is a governor who has spent years positioning himself to the left of Washington on climate, immigration, and civil rights, and who nonetheless will not touch a tax on roughly two hundred billionaires. The generous reading is that he genuinely believes the revenue projections are fantasy and the flight risk is real. The cynical reading is that a presidential hopeful cannot afford to be the man who signed off on a wealth tax that donors in Silicon Valley will remember forever.

Both readings can be true at once, and I suspect they are. What is undeniable is that Newsom's stance strips the measure of the establishment cover a normal California progressive initiative would enjoy. When the Democratic governor and the Democratic frontrunner to replace him both say no, proponents cannot pretend this is a routine soak the rich exercise.

The Sanders and Khanna oligarchy argument

On the other side stand figures who see Proposition 40 as a moral necessity. Senator Bernie Sanders endorsed the measure at a Los Angeles rally in February 2026, and Representative Ro Khanna, whose district sits in the heart of Silicon Valley, backs it too. Khanna has framed the billionaires resisting it as modern oligarchs, which is pointed language to aim at people who are, in some cases, his own constituents and donors.

Their strongest argument is not envy but arithmetic. Supporters contend the money is needed to offset federal healthcare cuts flowing from the 2025 One Big Beautiful Bill Act, cuts that land hardest on the low income Californians who use the state's health and education systems. In that framing, Proposition 40 is not punitive. It is a backfill for a hole Washington punched in the state budget, financed by the only people wealthy enough to plug it without anyone else noticing.

I find this the most persuasive case for the measure, and also the one proponents undersell. If the choice is genuinely between a 5% one time levy on two hundred billionaires and deep cuts to healthcare for millions, that is not a hard moral question. The trouble is that voters have learned to distrust ballot measures that promise painless money from someone else, and the exodus headlines make this one look precisely like that kind of promise.

The revenue math behind the $100 billion figure

Everything comes down to whether the $100 billion is real. The projection rests on roughly 200 to 214 people staying put and paying up. We already know six left and took an estimated $27 billion of the projection with them. The measure's defenders will say the January 1 anchor still captures those six, and legally they may be right. But every departure that survives a court challenge is revenue that never arrives, and every year of litigation is a year the hospitals and schools do not see the money.

There is also a behavioral question the models struggle to price. Wealth taxes on tiny, hyper mobile populations are notoriously hard to forecast because a small number of exits swings the total wildly. Lose ten more billionaires to Miami and Austin, and the $100 billion becomes $60 billion or less. The revenue is not a fixed pot; it is a function of how many of two hundred specific human beings decide California is worth staying for.

My honest assessment is that the true yield of this tax will land well below the headline figure, and that proponents would be wiser to campaign on a realistic number than to defend a projection the exodus has already dented. A tax that raises $50 billion for healthcare and education is still a generational transfer. Overselling it invites the disappointment that kills future measures.

A California experiment the rest of the country is watching

Strip away the personalities and Proposition 40 poses a question every wealthy democracy is quietly asking: can a government tax capital that can move faster than legislation? California is running the experiment in public, with named billionaires, a hard residency date, and an $82 million counter campaign, and the rest of the country is watching to see whether the door slams shut or the money simply flows around it.

I will not pretend to know how November goes. What I believe is that the exodus is being weaponized dishonestly by opponents who imply the tax is already beaten, and oversold dishonestly by supporters who cling to a $100 billion figure the math no longer supports. Voters deserve the version in between: a measure that will raise real money from real billionaires, less than promised, at the cost of a fight that will outlast the election.

If I had to plant a flag, I would say the principle behind Proposition 40 is defensible and the execution is flawed enough to worry me. Taxing two hundred people to fund healthcare for millions is not the outrage its opponents claim. But a measure whose success depends on the courts, the residency clause, and the personal loyalty of billionaires to a state they can leave in an afternoon is a fragile foundation for a hundred billion dollar promise. California voters should go in clear eyed about both.