Anti-tax advocates contend that higher taxes on the wealthy lead to millionaire flight. They say this has been seen in Maryland, Rhode Island, New Jersey and New York. The rich are mobile, they say. They can take their money, taxes and jobs wherever they are treated best.

But a new study focusing on New Jersey provides some of the most detailed evidence yet that so-called millionaire taxes have little effect on the movements of millionaires as a whole.

The...