According to a filing from Friday, Brin donated an additional $20 million to Building a Better California, a PAC and political advocacy organization opposing the state’s billionaire tax and supporting other pro-business policies and housing and infrastructure affordability. He has now given a total of $102 million to the group. 

Proposition 40, which will be on the ballot in November, would impose a one-time, 5% tax on California’s 200 billionaires, with 90% of the revenue from the proposed measure going toward the state’s healthcare program and 10% going toward education, food assistance, and administration. Brin, with a net worth of nearly $270 billion, could owe more than $13 billion as a result of the tax. 

California, the most populous state, has become the epicenter of the conversation around the K-shaped economy, or the diverging fortunes of those with wealth and those without it. While the Golden State has a $4 trillion GDP, making its economy about the same size as the United Kingdom’s, it also has 18% of its residents living below the poverty line, the highest in the country, in part because of its high cost of living.

Billionaires push back against Prop 40

The ballot measure has caused an uproar among some of California’s wealthiest individuals such as former Google CEO Eric Schmidt and PayPal co-founder Peter Thiel, both of whom have donated to organizations against the measure. Brin compared the proposal to his socialist Soviet upbringing.

“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,” he told the New York Times in a statement in April.

California Governor Gavin Newsom has joined these tech billionaires in combating the measure, arguing the tax would hurt the state by eroding its tax base, ultimately reducing key 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 to Prop 40 may in some ways be a self-fulfilling prophecy, as billionaires including Brin shift business entities out of California in favor of states without similar wealth taxes. Brin now lists Nevada as his residence, according to state records. Larry Page, who co-founded Google alongside Brin, has converted several of his assets out of California, including Koop, his family office, which was incorporated in Delaware in December 2025. Oceankind, an ocean science nonprofit founded by Page’s wife Lucy Southworth in 2018, was similarly incorporated in Delaware around the same time. Brin, for his own part, reportedly bought a $51 million home near Miami Beach in March. 

Will a wealth tax drain California? 

There’s not yet clear evidence to indicate these billionaires’ anxieties about the future of California are well-founded. On one hand, the six billionaires expected to leave California—Brin, Page, Thiel, as well as car loan magnate Don Hankey, former Uber CEO Travis Kalanick, and director Steven Spielberg—would have collectively generated about $27 billion in tax revenue, about one-fourth of the $100 billion the proposal is expected to raise through taxes over five years.

On the other hand, billionaires were already paying so little in California income tax that their departure may not pack as much of a punch as anticipated. A working paper published by the National Bureau of Economic Research in May noted that billionaires residing in the state paid $4.1 billion in income tax last year, about 0.2% of their collective $2 trillion net worth, meaning that even if every billionaire were to leave the state, it would take about 25 years for lost income tax revenue to cancel out the $100 billion sum California is projected to get from the tax. Even if a billionaire mass exodus included one-quarter of the state’s wealthiest residents, it would take a century to equal the $100 billion windfall.

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