If passed, this would be a huge incentive for the rich to avoid living in or even traveling to California, and not even so much for the amount of the tax as for the enormous decade-long legal, accounting, and compliance burden that would suddenly hook on to them like a barnacle. Every tax lawyer in the world would tell their clients that California is now radioactive: "touch it, and I'll be racking up $400 billable hours from now until your kids are in college".