a) thinking of actually leaving the state, or

b) thinking of telling their team of accountants to claim on tax paperwork that their permanent residence is in another state

because things like this make me think it's the latter:

> In mid-December, three limited liability companies associated with Mr. Page filed documents to incorporate in Florida, according to state records.

at the amount of wealth we're talking about, it's trivial for a billionaire to buy an additional mansion in (Florida|Texas|Nevada|Wyoming|etc), and claim that as their "official" residence.

if they get billed with a wealth tax, their team of lawyers will claim that they live in that other state, and simply happen to spend a huge amount of their time on "business trips" to California.

so the success or failure of this will hinge on how thoroughly it's actually enforced. the "progressive" Governor Newsom is opposed to it:

> The measure faces opposition from Silicon Valley investors and others, including Gov. Gavin Newsom. At The New York Times DealBook conference this month, Mr. Newsom said a wealth tax was not pragmatic. The Democrat, who has been close with people like Mr. Page, is raising money for a committee to oppose the measure. The committee received a $100,000 donation from the venture capitalist Ron Conway in November, according to state campaign finance records.

which makes me think that even if it does pass, he won't make enforcement of it a priority (especially since he'll be busy running for President)

One idea: start progressively increasing property tax on homes over 10,000 sq.ft. - now billionaires can have their huge mansions but will need to pay double-digit percent property tax for it.