Sergey Brin spends $102m to fight California billionaire tax

Google co-founder Sergey Brin has poured $102 million into a campaign to defeat a proposed California wealth tax that would cost him an estimated $13 billion.

Campaign filings show Brin is the largest single donor opposing Proposition 40, which goes before the state's voters in November. His donations have gone to Building a Better California, a political action committee and advocacy group fighting the ballot measure.

The fight has drawn enormous sums from Silicon Valley's elite, reflecting a deep divide over how the state should address its stark wealth inequality.

What is Proposition 40?

The ballot measure proposes a one-time 5 per cent tax on California’s 200 billionaires, with the payments spread over five years.

If passed, the state expects the tax to raise about $100 billion. The vast majority of this money—90 per cent—is earmarked for California’s healthcare system. The remaining 10 per cent would fund education, food assistance, and administrative costs.

For Brin, whose net worth is estimated at nearly $260 billion, the financial stakes are higher than for almost anyone else. A 5 per cent levy on his fortune would result in a tax bill of roughly $13 billion.

The threat of that bill has triggered a massive spending counter-offensive. Opponents of the tax have raised more than $187 million, easily eclipsing the $32 million raised by the measure's supporters.

Why tech billionaires are fighting back

Brin is not the only high-profile figure putting money into the opposition. Former Google chief executive Eric Schmidt and PayPal co-founder Peter Thiel have also donated to groups fighting the proposal.

In a statement to the New York Times in April, Brin linked his opposition to his family’s flight from the Soviet Union when he was a child. 'I fled socialism with my family in 1979 and know the devastating, oppressive society it created,' he said. 'I don’t want California to end up in the same place.'

The tech billionaires have found an unlikely ally in California Governor Gavin Newsom. The Democratic governor has campaigned against the wealth tax, arguing that taxing the ultra-rich too heavily will ultimately erode the state's tax base and shrink the revenue available for schools, childcare, police, and firefighting.

That migration is already happening, at least on paper. State records show Brin now lists Nevada as his residence, and he recently bought a $51 million home near Miami Beach. Larry Page, who co-founded Google with Brin, has also begun moving assets out of the state, incorporating his family office and his wife’s ocean science non-profit in Delaware.

Would a wealth tax drain the state?

The argument that taxing billionaires will cause a ruinous 'tax flight' is central to the opposition campaign. If the six wealthiest individuals expected to leave—including Brin, Page, Thiel, and tech investor Don Hankey—were to depart, the state would lose about $27 billion in projected revenue from the wealth tax itself.

However, a working paper published in May by the National Bureau of Economic Research suggests the broader financial impact of these departures might be exaggerated.

According to the paper, California’s billionaires paid $4.1 billion in state income tax last year, representing just 0.2 per cent of their combined $2 trillion net worth.

Because their current annual tax contributions are so low relative to their total wealth, the researchers calculated that even if every single billionaire left California, it would take 25 years of lost income tax to offset the $100 billion the new wealth tax is projected to raise. If a quarter of those billionaires left, it would take a century for the lost income tax to match the windfall.