Google cofounder Sergey Brin has spent over $100M to oppose California's billionaire tax. Here's how much he could lose if the proposal is passed

Google cofounder Sergey Brin has now spent more than a hundred million dollars to fight the state of California's proposed tax on billionaires. According to official filings, Brin has donated as much as $102 million to Building a Better California, a political advocacy organization opposing the proposed wealth tax and supporting other pro-business policies. This makes Brin, the 53-year-old former president of Google's parent company Alphabet, the largest individual contributor to the effort to block the tax measure.

What is the billionaire tax?

The initiative, called Proposition 40, would levy a one-time 5 percent tax on California's 200 billionaires, with 90 percent of the revenue going towards the state's healthcare program. The remaining 10 percent funds would support education, food assistance, and administration. Proposition 40 will be on the ballot in November.

Why has it been introduced?

California, which is the most populous US state with 39.5 million people, has become a symbol of wealth inequity. While the western state has a gross domestic product (GDP) of $4 trillion -- an economy as large as the United Kingdom's -- 18 percent of its residents live below the poverty line. That figure is the highest of all states, partly because of the Golden State's high cost of living.

How wealthy is Sergey Brin?

Sergey Brin, who remains a controlling shareholder and board member at Alphabet, has a net worth of over $259 billion, making him the fifth wealthiest person in the world, according to the latest figures from Forbes. This means that he could owe about $13 billion if California's wealth tax is implemented.

Speaking about his opposition to the proposal, Brin, who was born in Russia, had told the New York Times in April: "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."

Billionaires move out of California

Several billionaires, including Brin, are moving businesses to states with no such wealth taxes. Brin now lists Nevada as his residence, according to state records. In March, he purchased a $51 million house near Miami Beach in Florida. His cofounder at Google, Larry Page, has converted several of his assets out of California, including his family office Koop, which was incorporated in Delaware last year. Oceankind, an ocean science nonprofit founded by Page’s wife Lucy Southworth in 2018, was also incorporated in Delaware around that time.