If approved by voters, the one-time 5% tax on billionaire wealth would hit around 200 ultra-rich residents. Backers of a new tax on California billionaires appear to have gathered more than enough signatures to put the proposal on the ballot this fall, escalating a battle between the state’s labor unions and its richest residents. The labor coalition behind the initiative said at a press conference Friday that more than 1.5 million Californians had signed the petition calling for a one-time 5%