Other US states — including Washington state, Maine and Minnesota — have passed or are considering similar income or wealth tax measures.In the United Kingdom, a group of 120 millionaires have launched a “Proud to Pay” campaign asking the government to levy an additional 2% tax on wealth over £10 million.Behind the public discussion of California’s billionaire tax lies a much deeper debate about spiralling global inequality.Recent data from the US shows the share of economic output flowing to workers has dropped to a record low of 52.9 per cent in 2026 Billionaires, the most obvious and visible symbol of global wealth inequalities, are an obvious target.However, as California’s proposal shows, attempts to rein in the wealth and power of billionaires should expect furious backlash from billionaires themselves.In addition to Brin’s US$100 million, other billionaire donors including Peter Thiel, Eric Schmidt and Chris Larsen have also spent significantly to oppose the tax