Of course the number of millionaires has grown on an absolute basis given inflation and the strong stock market.
To control for this look at NYC's share of the nation's millionaires, which shrank from 6.5% in 2010 to 4.2% in 2022.
https://cbcny.org/research/hidden-cost-new-yorks-shrinking-m...
Okay, so aggressive taxation should then have its (proven) benefits weighed against the (dubious) benefits of having 30% of your millionaires change their legal residence to be elsewhere.
I think taxes still handily win with room to spare. Even more: plenty of those rich people are still in NY and participating in its economy (legal residence != where you actually physically live, especially if you have resources to game residence by owning multiple properties).