In a video posted on Tuesday by the NYC Mayor’s Office, Mamdani announced the city’s first-ever pied-à-terre tax: an annual fee on luxury properties valued above $5 million whose owners do not live in New York full-time. The video, which has already drawn nearly 470,000 views and 48,000 likes, was shot outside 220 Central Park South, the building where Citadel CEO Ken Griffin owns a four-floor penthouse he purchased in 2019 for $238 million, then the highest price ever paid for a home in the United States.

“When I ran for mayor, I said I was going to tax the rich,” Mamdani said in the one-minute clip. “Well, today we’re taxing the rich.”

The proposal, which is backed by Gov. Kathy Hochul and still requires approval from the state legislature, would apply to one-to-three-family homes, condominiums, and co-ops worth over $5 million when the owner’s primary residence is outside New York City. Mamdani’s office estimates the tax would generate at least $500 million annually, with revenue directed toward free childcare, street cleaning, and neighborhood safety.

Griffin relocated Citadel’s headquarters from Chicago to Miami in 2022, drawn by Florida’s lack of a personal income tax. He shares the move with Jeff Bezos, Mark Zuckerberg, and Google cofounders Larry Page and Sergey Brin, all of whom recently left high-tax states and now maintain Florida residences. Griffin also recently paid $38 million for a duplex apartment up the block from where Mamdani shot the video, according to the Wall Street Journal.

Mamdani said the tax would fix “a fundamentally unfair system.” “These units are sitting empty,” he said. “And even so, they’re able to reap the huge financial rewards of owning property in, dare I say, the greatest city in the world.”

The pied-à-terre tax has circulated in New York policy circles for years but has repeatedly stalled in Albany. Mamdani recently pushed a wealth tax in New York but said the city would be forced to instead increase property taxes if the tax didn’t get state approval. Neither Griffin nor the mayor’s office responded to Fortune’s request for comment.

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