Here’s what really happens when states raise taxes on millionaires – Crain’s*

The question now: How likely is a massive flight of millionaires if Illinois voters approve the proposed constitutional amendment allowing graduated tax rates? The experience of other states that have jacked up taxes on the wealthy offers some insight. While millionaires haven't abandoned those states en masse, there's some evidence that the loss of a small number of top earners can have a big impact on the revenue generated by such a hike.