Bill Ackman rushes to defend Ken Griffin's $238M NYC penthouse from Zohran Mamdani’s vacant luxury home tax: 'We should be applauding Ken'

Mamdani mentions Ken Griffin, CEO of the hedge fund Citadel LLC, by name in the announcement video. For much of the video, Mamdani stands outside Griffin's $238 million penthouse, which the mayor says largely sits unused.

In an April 16 post on X, fellow hedge fund manager Bill Ackman came to Griffin's defense, saying "we should be applauding Ken."

Here's why Ackman disagrees with Mamdani's tax, and why New York Governor Kathy Hochul is joining the mayor in his effort.

Why is New York City implementing a pied-à-terre tax?

This new wealth tax is a pied-à-terre tax, or a tax on secondary residences (2). It won't apply to primary residences, nor will it apply to secondary residences that are being used as rental properties, according to Governor Hochul (3). If someone is using the residence, no matter who it is, the tax doesn't apply.

This would be the first time a pied-à-terre tax is implemented in New York City, but it isn't the first time one was proposed. A similar tax was put forth in 2019, but it ultimately failed to pass (4).

Hochul calls the tax a "common-sense surcharge" and says it will help shore up the budget gap that New York City is currently facing (5).

The governor compares it directly to other budget proposals that she doesn't support, such as raising income taxes on residents or taxes on corporations. She says these taxes could drive people or corporations out of the city, which she wants to avoid. This is likely in reference to Mamdani's campaign promise to push for an increase on corporate taxes, as well as taxes on New Yorkers making more than $1 million annually (6).

She says that people who own these secondary residences are benefitting from New York City's strengths through rising property values, but they aren't contributing back in turn. The buildings are "part of our skyline, but those people are not part of our city," she says.

"It's a matter of fairness to all those millions of residents who actually live here."

Many of the tax's details aren't hammered down just yet, but it will likely be a yearly fee based on the value of the residence (7).