The honest conclusion is narrower than either slogan: Massachusetts has an outmigration problem, but the millionaire’s tax has not yet been shown to be the cause of a millionaire exodus.
Millionaires are not as footloose as advertised
The broader research also cuts against the simplest version of the tax-flight story.
Cristobal Young and other researchers have studied millionaire migration using administrative tax data. Their work found that millionaires do move, but not nearly at the scale often imagined in political debate. In one model, eliminating state tax differences would reduce predicted millionaire migration only slightly — suggesting that a small share of elite migration is driven by income-tax differences alone.
That finding makes intuitive sense. Very high earners are often tied to the places where they earn their money. They own businesses. They sit on boards. They have clients, law firms, hospitals, universities, donors, social networks, and family connections. They may own a second home in Florida. That does not mean they can effortlessly move their economic life there.
There are exceptions. Retirees can move more easily. Investors can move more easily than surgeons, lawyers, founders still operating companies, or executives tied to headquarters. Remote work has changed some calculations. So has the rise of no-income-tax states aggressively courting wealth.
But the image of the millionaire as a frictionless tax particle is overstated. Wealth gives people options. It does not erase all attachments.
A national tax changes the geography
This is where the Massachusetts story becomes a national one.
A state surtax creates an obvious escape route: change domicile. If Massachusetts taxes million-dollar income and Florida does not, moving from Boston to Miami may reduce the state tax bill. The move can be real, or it can be half-real, producing fights over domicile, days spent in each state, home ownership, family location, voting registration, doctors, clubs, and the other small facts that reveal where a person actually lives.
A national surtax changes that.
If Congress imposed a federal tax on income above $1 million, moving from Massachusetts to Florida would not avoid the federal tax. It might still avoid Massachusetts tax. It might reduce state income tax. It might reduce estate-tax exposure. But it would not move the taxpayer outside the national surtax.
That is the strongest argument for doing this kind of tax federally rather than state by state. A national tax has a broader base, a larger enforcement agency, and less exposure to interstate tax competition. It closes the easy door.
It does not close every door.
A federal surtax would shift the avoidance strategy from geography to accounting. High-income taxpayers could still defer capital gains, change the timing of income, shift compensation into equity, borrow against appreciated assets, use trusts, make charitable gifts, alter business structures, or seek ways to convert ordinary income into capital gains. A few might consider foreign residence or expatriation, though U.S.