New York's millionaire count grew 48% in the five years through its 2021 rate increase

That 21% was measured off 2020, not 2019. New York's tax department counted 57,126 million-dollar earners in 2016 and 68,068 in 2019, according to a Fiscal Policy Institute fact sheet ^[9]. Growth of 21% into 84,366 implies a 2020 base near 69,700 ^[1]. From 2016 to 2021 the count grew 48% ^[2].

Departures are the cleaner measure, because the number of million-dollar earners rises whenever incomes rise and not only when people arrive. The 1,453 who left in 2021 were 1.7% of that year's count, and the roughly 2,000 who left the year before were 2.9% of the implied base ^[3].

"We're just really not seeing any declines in the millionaire population in New York State," Emily Eisner, executive director of the Fiscal Policy Institute, told Fortune ^[5]. She said millionaire households "simply just aren't that sensitive to the tax rates in the state" because "the taxes aren't really high enough for them to be sensitive to them" ^[6]. Where the burden does land hardest, the institute puts it on families earning between $100,000 and $500,000 a year ^[7]. "You're making a lot of money relative to the population of the United States, but in New York City, you don't feel rich at all. You still feel squeezed," Eisner said ^[8].

Opponents of the 2012 vote that took the top rate to 13.3% said the rich were already packing ^[15]; 138 departures out of 312,000 filers subject to the rate is one filer in about 2,260 ^[4]. The institute reports the state's millionaire population kept growing ^[17].

The live counter-argument now runs through growth instead of flight, and its author bounds it himself. "States tend to grow about a percentage point faster for five, six years, and then they return to trend," Adam N. Michel, who wrote the Cato Institute paper, told Fortune ^[22]. The results are insignificant after year 10 ^[21]. Colorado, which switched in 1987, had per capita income about 5% above comparable states a decade later ^[23]. Eisner, asked about the paper, said "the timing of these changes is nowhere close to random" ^[25]. Colorado's Prop 87 asks voters this year whether to return to a graduated system ^[24].

At the rates on the books, in the six jurisdictions the institute measured, counts have risen since 2010 ^[2]. The most recent year reads the same: New York's millionaire share rose again in 2023 while Florida's declined ^[3][4]. That is a narrow claim. In my view it holds for California at 13.3% and for New York after 2021, and it holds only for rates that are on the books. What would overturn it is several consecutive years of falling counts in New York and California while Florida's share climbs. New York expanded its mansion tax in 2019 on a scale rising to 3.9% on sales above $25 million ^[14], and the count kept climbing ^[13].