Google’s Sergey Brin has donated more than $100 million to oppose California’s billionaires tax.

According to filings, Brin donated a total of $102 million to the group Building a Better California, a PAC and political advocacy organization opposing the state’s billionaire tax and supporting other pro-business and pro-housing and infrastructure affordability policies. Campaign records show efforts to block the tax exceeded $187 million, making Brin the largest single contributor to the effort. Contributions in support of the bill have since reached approximately $32 million.

Proposition 40, which will be voted on in November, would impose a one-time 5 percent tax on California’s 200 billionaires, with 90 percent of the proposed measure’s revenue going to the state’s health care program and 10 percent to education, food assistance and administration. Brin, with a net worth of nearly $260 billion, could owe about $13 billion because of this tax.

California, the most populous state, has become the epicenter of discussions around the K-shaped economy, or the divergent fortunes of those who have wealth and those who do not. Even though the Golden State has a GDP of $4 trillion, making its economy roughly the same size as the United Kingdom’s, 18 percent of its residents live below the poverty line, the highest in the country, in part because of its high cost of living.

Who are the billionaires who oppose Prop 40??

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

“I fled socialism with my family in 1979 and I know the devastating and oppressive society it created in the Soviet Union. I don’t want California to end up in the same place,” he told the newspaper. New York Times in a press release in April.

California Governor Gavin Newsom joined these tech billionaires in fighting the measure, arguing that the tax would harm the state by eroding its tax base, thereby reducing key social service revenues.

“The fact is, this will actually reduce investment in education,” Newsom said in a statement. Bloomberg Business Week interview earlier this year. “It will reduce investments in teachers, librarians and child care. It will reduce investments in firefighting and policing.”

Opposition to Proposition 40 could, in some ways, be a self-fulfilling prophecy, as billionaires including Brin move their 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 many 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 also incorporated in Delaware around the same time. Brin, for his part, reportedly purchased a $51 million home near Miami Beach in March.

Will a wealth tax deplete California?

There is no clear evidence yet that these billionaires’ concerns about California’s future are founded. On one hand, the six billionaires expected to leave California — Brin, Page, Thiel, along with auto loan magnate Don Hankey, former Uber CEO Travis Kalanick and executive Steven Spielberg — would have collectively generated about $27 billion in tax revenue, or about a quarter of the $100 billion the proposal is expected to raise through taxes over five years.

On the other hand, billionaires already paid so little income tax in California that their departure might not have as much effect as expected. A working paper released in May by the National Bureau of Economic Research indicated that billionaires residing in the state paid $4.1 billion in income taxes last year, or about 0.2 percent of their collective net worth of $2 trillion, meaning that even if every billionaire were to leave the state, it would take about 25 years for the loss in tax revenue to offset the $100 billion that California stands to gain from this. tax. Even if a mass exodus of billionaires included a quarter of the state’s wealthiest residents, it would take a century to reach the $100 billion windfall.

“California billionaires’ proposed one-time tax of 5 percent, payable over five years, is both small relative to California billionaires’ wealth gains and large relative to the taxes they currently pay,” the authors write.

A version of this story was published on Fortune.com on August 11, 2026.

Learn more about California’s billionaire tax:

• A consultant who once attacked the “billionaire boys club” is now leading the opposition to California’s wealth tax.
• California billionaires tax will ‘start a movement’ that will spread to more states, federal government and other countries, Nobel laureates say
• The tax avoidance map: Billionaires rush to Florida from the West Coast, taking with them some $29 billion in tax revenue