But if they do choose to leave, or at least stop expanding their businesses, you can’t deny the rational self interest
We've done fine without them in the past, and we'd be better off without them now. At the end of the day, labor and its fruits are the primary origin of value in an economy, not the handful of individuals that have had the immense luck and/or dubious ethics required to capture that value for their personal gain.
"If you tax the rich, they will leave" is a myth created by the rich so that you won't tax them.
In the middle of the 1900s, the tax rate on the wealthiest Americans was 91%.
Nobody is going to leave over Mamdani's extremely modest proposal.
You forgot to mention that only half of capital gains were subject to tax. So the highest marginal rate was 45.5%.
1) That we're at the threshold for taxes that the wealthy will accept. I would bet many wealthy folks feel attached to their homes as their identity, and it would take some amount to price them out. Like, clearly a billionaire would leave if the cost to stay was a 100% of their wealth, but would probably stay if it was $10 more in taxes. So there's a very nebulous line somewhere in between. I suspect we are not close to that line.
2) That wealthy people living in an area are storing their wealth or declaring that area as their home. Plenty of ways to shield wealth from local taxes, and plenty of ways to claim a place as your home without being taxed by it.
3) That having wealthy people in your community is a net positive for the community. Wealthy people tend to use a lot more resources and distort local politics for their personal gain rather than the gain of the community. Maybe we'd be better off if they weren't around, and several families moved in to take their place. Wealthy people don't ride public transit, normal folks do. Wealthy people can push city council positions to reduce transit, normal folks don't have that influence. Maybe we need more normal folks around.
4) That businesses owned by the wealthy are a net positive compared to, e.g., workers co-ops. Maybe we could be a bit more collective in our approaches and a bit less lionizing towards the wealthy person who got lucky. Maybe we need more community oriented businesses run by members of the community they live in and fewer wealthy business owners racing to the bottom.
In any case, this is all a major deflection resulting from the lie that the low job creation rate is due to "the threat" of a possible future mayor rather than tariffs.