The $100bn needs $2tn in state: California's billionaire tax is eroding its own base

Begin with the base, not the headline. A one-time 5% levy that raises $100 billion requires $2 trillion of net worth sitting in California on the assessment date, spread across the roughly 200 people the bill is said to reach, an average of $10 billion each ^[14]. Larry Page and Sergey Brin, at $295 billion and $275 billion, were 28.5% of that base between them ^[15]. Both left before Jan. 1 ^[4].

Fortune's estimate of what walked is conservative on its own inputs. Five percent of $570 billion is $28.5 billion, not the $27 billion implied by its rounded per-head figures of about $14 billion and $13 billion; add the $1.8 billion it attributes to Travis Kalanick and Peter Thiel and the hole is closer to $30.3 billion ^[16]. Against a $100 billion target that is 29% before rounding ^[18], and it is 29% of a base that has not yet been assessed.

The price of resistance is the other number worth writing down. Brin has put $102 million into Building a Better California, a PAC promoting three counter measures that could kill the billionaire tax on arrival even if voters approve it ^[7]. Measured against the $13.75 billion that 5% of his stated net worth would produce, that is about 0.7% ^[17]. He has bought the exit and the option, and the option cost less than one percent of the liability. Thiel's $3 million to the California Business Roundtable sits in the same range ^[8].

The mechanism is unglamorous: the measure keys liability to residence in California after a fixed date ^[1], which makes the date the only term in the formula the payer controls. Washington shows the alternative. Governor Bob Ferguson signed a 9.9% tax on earnings above $1 million in March, aiming at $3 billion to $4 billion a year, after Jeff Bezos and Howard Schultz had already left Seattle ^[10]. An income tax recurs, so departures cost the state every year; California's single assessment is worth 25 to 33 years of Washington's annual target ^[19], and it can be defeated once, by moving once.

Attribution is messier than the flight narrative allows. Ken Griffin moved Citadel from Chicago to Miami in June 2022 and pointed to the city's crime and politics ^[11]. Florida levies no income tax and no capital gains tax, which was true before any of these proposals ^[12], and Miami's ultra-luxury market recorded 361 sales at the $10 million level in 2025 ^[13]. What distinguishes Page, Brin and Kalanick is not the destination but the timing: their moves cluster against a statutory date ^[4][5].

So the argument between legislators and wealth managers is no longer about whether a 5% levy is constitutional or popular. Voters are split 48% to 41% in the UC Berkeley Institute of Governmental Studies poll ^[9], and a simple majority in November would amend the constitution ^[3]. Passage decides whether the tax exists. The base decides what it collects, and a static $2 trillion is now the wrong input.