The study you cite came in for tons of criticism as soon as it came out, and has largely disappeared from view as a result. It was biased in who initiated it (State Franchise Tax Board), and who researched it.
Its main flaw was to draw a sweeping conclusion from too little data. To change the tax rate by 1% and then ascribe millionaires’ moving pattern changes, or lack thereof, to the tax change is quite a leap. Many other factors weigh far more in the decision, particularly where we are in the business cycle. The dot-com boom of the 1990s and the RE boom and bust of the middle of the last decade affect moving decisions into or out of the state by the wealthy far more than tiny changes in taxes.
And the last change in marginal tax rates from about 10% to about 13% wasn’t so tiny. It will likely be the last straw for many wealthy Californians. It will be interesting to see the results, which should be apparent in the very near future.
