The nice thing about economics is how unreplicable it is due to exogenous circumstances.

It will be interesting to see how many very successful people decide they don't want to supply even more of the tax base.

"Second, the proponents’ 10 percent avoidance assumption is obsolete before signatures have even been submitted. Between the initiatives announcement on October 15, 2025 and the residency snapshot date of January 1, 2026, just six publicly confirmed departures eliminated far more than 10 percent of the base. During this period, nearly 30 percent of California’s wealth tax base left the state, and this only includes the billionaires who publicly announced their departures (see Table 1). "

https://libertylensecon.substack.com/p/california-wealth-tax...

Unlike in New York City, though, billionaires don't contribute that much to a total income tax receipts- a little over 2%, though that is from about 150 households, so anybody moving will have necessarily a significant impact.

https://www.nber.org/papers/w35218

https://www.ntu.org/foundation/detail/leave-if-you-tax-them-...