No, it's simply that a threshold exists at which people will move, and it hasn't been reached yet. Like most of the problems discussed in the economic reality article, this is a tradeoff -- people have clearly decided that they are willing to put up with higher taxes to live in New York instead of New Jersey. But surely you can see that there is a point at which it won't be worth it for many people.

Well, the sheer deluge of articles proclaiming an impending exodus every time the idea of raising taxes is mooted and the lack of any evidence for these so called exoduses has made me... skeptical.

Historically the highest US income tax rate was 95%. Guess what?

It only takes a few one-percenters moving away from a state to drain tens, or even hundreds, of millions of dollars from the state's tax revenue. I think this was mentioned in the article: http://www.nytimes.com/2016/05/01/business/one-top-taxpayer-...