Sergey Brin Has Spent $102 Million Fighting California's Billionaire Tax

Sergey Brin has spent $102 million to block California's proposed billionaire tax—a measure that could cost the Google cofounder roughly $13 billion if voters approve it in November.

According to state filings, Brin donated the total to Building a Better California, a PAC and political advocacy organization opposing the tax and backing pro-business policies plus housing and infrastructure affordability. Campaign filings show the effort to defeat the measure has raised more than $187 million, making Brin its largest sole contributor. Supporters have gathered about $32 million.

What Would Proposition 40 Do?

The ballot measure would impose a one-time 5% tax on California's 200 billionaires. Ninety percent of the revenue would go to the state's health care program; the remaining 10% would fund education, food assistance, and administration.

Brin, with a net worth of nearly $260 billion, could owe about $13 billion.

The vote lands in a state that has become the epicenter of the debate over the K-shaped economy—the diverging fortunes of the wealthy and everyone else. California's $4 trillion GDP roughly matches the United Kingdom's, yet 18% of its residents live below the poverty line, the highest share in the country, driven in part by high living costs.

Who Are the Billionaires Pushing Back?

The measure has drawn fierce resistance from some of California's wealthiest residents, including former Google CEO Eric Schmidt and PayPal cofounder Peter Thiel, both of whom have donated to opposition groups. Brin has framed the fight in personal terms.

"I fled socialism with my family in 1979 and know the devastating, oppressive society it created in the Soviet Union. I don't want California to end up in the same place," Brin told the New York Times in a statement in April.

Governor Gavin Newsom has joined the opposition, arguing the tax would erode the state's tax base and ultimately cut revenue for social services.

"The fact is it actually will reduce investments in education," Newsom said in a Bloomberg Businessweek interview earlier this year. "It will reduce investments in teachers and librarians, childcare. It will reduce investments in firefighting and police."

The opposition may prove partly self-fulfilling. Billionaires including Brin have already shifted business entities out of California to states without similar wealth taxes:

• Brin now lists Nevada as his residence, according to state records.
• Larry Page converted several assets out of California, including Koop, his family office, incorporated in Delaware in December 2025.
• Oceankind, the ocean science nonprofit founded by Page's wife, Lucy Southworth, in 2018, was incorporated in Delaware around the same time.
• Brin reportedly bought a $51 million home near Miami Beach in March.

Will a Wealth Tax Drain California?

The evidence so far does not clearly support the billionaires' warnings.

On one hand, the six billionaires expected to leave the state—Brin, Page, Thiel, car loan magnate Don Hankey, former Uber CEO Travis Kalanick, and director Steven Spielberg—would have collectively generated about $27 billion in tax revenue. That equals roughly one-fourth of the $100 billion the proposal is projected to raise over five years.

On the other hand, billionaires were already paying so little in California income tax that their departures may not pack the anticipated punch. A working paper published by the National Bureau of Economic Research in May found billionaires residing in the state paid $4.1 billion in income tax last year—about 0.2% of their collective $2 trillion net worth. Even if every billionaire left, it would take about 25 years for lost income tax revenue to cancel out the $100 billion the tax is projected to raise. If one-quarter of the state's wealthiest residents departed, it would take a century to match the $100 billion windfall.

"The proposed one-off California billionaire tax of 5%, payable over five years, is both small relative to California billionaires' wealth gains and large relative to the taxes they currently pay," the NBER authors wrote.

With Brin's $102 million already deployed and the vote set for November, the most expensive ballot-measure fight of the cycle will test whether California's voters see its 200 billionaires as the state's fiscal backbone or its undertaxed outlier.