A little more than 200 people could decide how California pays for its hospitals. That is roughly the number of billionaires who live in the state, and Proposition 40 would ask each of them for a single payment equal to 5% of their net worth. Supporters hope the measure will raise $100bn (£75bn). The list of residents it would affect includes Oprah Winfrey, Mark Zuckerberg, Kim Kardashian and George Lucas.
The scale of the numbers explains why the vote matters beyond America. California's economy is the largest in the United States and the fourth largest in the world, bigger than those of India and the UK. Yet the state also has the biggest share of homeless people in the country and one of the widest wealth gaps. Francesco Trebbi, a public policy professor at the University of California, Berkeley, believes this is the first wealth tax aimed at such an extreme slice of the distribution.
If it passes, it will become a test case that other governments, from Europe to Latin America, are likely to study closely. The immediate motive is financial rather than philosophical. Backers, led by the healthcare union SEIU-UHW, argue that federal funding cuts linked to President Donald Trump's tax and spending bill will leave a hole in the state's health system. Suzanne Jimenez, the union's chief of staff, calls the levy a short-term fix while a lasting solution is found.