California voters have rejected Proposition 40, the one-time 5% tax on residents with assets over $1 billion, handing tech's wealthiest founders a decisive win at the polls on Monday.

The numbers tell you how much they wanted it. Opposition committees reported about $130 million in contributions through October 22, per state campaign-finance filings. Supporters raised about $33 million. That's roughly a four-to-one spending gap, and it worked.

The measure would have hit 214 people — California's billionaire population as of January 1, 2026, according to Forbes data compiled by Americans for Tax Fairness, a group advocating higher taxes. Supporters claimed it would raise over $100 billion for the state. Opponents warned it would trigger a wealth exodus.

Who paid to kill it?

The opposition campaign drew heavily from Silicon Valley's top ranks. Google cofounder Sergey Brin, former Google CEO Eric Schmidt, Affirm CEO Max Levchin, Stripe CEO Patrick Collison, DoorDash CEO Tony Xu, Kleiner Perkins Chairman John Doerr, and angel investor Chris Larsen collectively poured millions into the "No" effort. Brin alone donated more than $100 million, per CalMatters.

That wasn't just check-writing. It was contingency planning too. Brin and fellow Google cofounder Larry Page moved entities tied to them out of California in December, as Business Insider first reported. Meta CEO Mark Zuckerberg weighed relocating out of the state. In October, Meta announced a new class of shares giving Zuckerberg $20 billion in what the company called "immediate liquidity" — potentially enough to pay the tax without diluting his voting power.

Not every billionaire flinched, though. "I've got to tell you, I have not even thought about it once," Nvidia CEO Jensen Huang said on Bloomberg TV in January. "We chose to live in Silicon Valley, and whatever taxes they would like to apply, so be it. I'm perfectly fine with it."

The vote also scrambled usual political lines. Vermont Senator Bernie Sanders backed the tax. California's Democratic Governor Gavin Newsom opposed it.

How would the tax have worked?

Prop 40 was a one-time levy, not an annual one. Taxable wealth would have included ownership stakes in businesses, securities, investment accounts, art, collectibles, and intellectual property. Real estate, pensions, and retirement accounts would generally have been excluded.

Payment was due in 2027, though taxpayers could have spread the cost across five years at a higher price.

Backers pitched the revenue as a lifeline. A majority of proceeds were earmarked for healthcare, with the rest going to education, food assistance, and administering the tax program itself. Supporters framed it as a way to backfill looming federal cuts to Medi-Cal, California's Medicaid program.

What does the economics say?

A National Bureau of Economic Research working paper from Stanford economists, published in October, cut against the optimistic math. The initial tax event would bring in around $30 billion, the authors estimated — far short of the $100 billion-plus headline. Worse, by prompting high-earning executives to leave the state, the paper projected a net loss of $38.9 billion.

So even the raise-the-money case was contested before voters weighed in. The mechanism is simple: a one-time levy gives people a single, enormous incentive to move their tax residence before the trigger date. The Stanford paper's model says enough of them would have acted on it.

Did voters even get a clean choice?

Not quite. Two companion measures, Props. 41 and 42, were designed to undercut Prop 40 by imposing new restrictions on state taxes. Even if Prop 40 had passed, either counter-measure could have blocked it by winning more "Yes" votes. Voters were, in effect, offered multiple simultaneous paths to "No."

What happens now?

California's 200-plus billionaires stay where they are, tax-wise. The state keeps its current structure, and the activists who spent three years building the campaign return to the drawing board. For the tech executives who spent nine figures defending their fortunes, the return on that investment arrived in a single night of vote-counting.