India, Aug. 18 -- California's November vote on a one-off 5% tax on billionaire wealth has become a global test of whether democracies can curb extreme riches amid spiralling inequality.

Backers say the $100 billion raised would fund healthcare, food aid and schools, while opponents warn billionaires will flee.

The battle reflects wider debates over unions, monopoly power and the future of AI-driven capitalism.

In November, California will vote on a proposal to levy a one-off 5 per cent tax on the wealth of all billionaires in the state.

Google co-founder and billionaire Sergey Brin has already spent $100 million on political donations to a group opposing the tax. Brin is hoping to avoid a potential tax bill of $13 billion, a return o...