The billionaire tax is an experiment, they did put the bar pretty high to measure how many families will relocate (that's super easy to track); once that's measured, it's easy to build a model to adjust this threshold to whatever is advantageous for the state and keep things in balance this way, where the outflow is carefully measured and weighted against the tax threshold. The "hard part" was just getting this to pass the vote; then they can adjust this threshold anytime as voters have already approved it. What isn't measured is that billionaires create jobs "around them"; and, implicitly, jobs will be created somewhere else; unfortunately this model will not measure that.