I think it's really hard to get accurate figures here.
Clearly a lot of major CA employers choose to put factories or large operations in other states for cost reasons; some of this may be regulatory, some may be taxes, some may be availability of labor, some may be availability of other resources (cheap power in OR/WA, old industrial facilities to repurpose, ...).
I don't think a lot of companies move their HQs from California to elsewhere, but you could easily have a much bigger effect from California-HQ companies putting their major new facilities out of the state.
I personally would like to put my business in Washington, Nevada, Hong Kong, maybe Texas, or potentially Colorado or Montana, for a mix of tax, regulatory, and cost reasons. Unfortunately, with the possible exception of Seattle, there's really no way to reliably locally hire enough computer security people, or to have proximity to customers, to overcome the advantage of the Bay Area. The alternative is some kind of distributed company, or recruiting and relocating lots of people, but that makes the difficult problem of a startup even harder.