Billionaire investor Bill Ackman is ringing the alarm over President Donald Trump’s latest tariff policy, calling it a dangerous move based on flawed calculations.
“The formula used by the administration to calculate tariffs made other nations’ tariffs appear four times larger than they actually are,” Ackman posted on X on Monday.
He said this mistake could have serious global consequences and warned that the U.S. economy might suffer as a result.
“President Donald Trump is not an economist and therefore relies on his advisors to do these calculations so he can determine policy,” Ackman said.
“The global economy is being taken down because of bad math.”
He urged Trump’s advisors to own up to the error and change course before April 9, adding, “The President’s advisors need to acknowledge their error… before the President makes a big mistake based on bad math.”
Flawed Tariff Math
According to journalist James Surowiecki, the White House may have used an oversimplified and misleading method: taking the U.S. trade deficit with a country and dividing it by that country’s exports to the U.S.
Using that logic, the U.S.’s $235.6 billion trade deficit with the European Union and the EU’s $605.8 billion in exports results in a made-up 39% tariff basis.
Trump reportedly called that figure “kind.”
Critics pointed out the administration’s published formula, meant to add credibility, included Greek letters and academic jargon but essentially amounted to the same back-of-the-napkin math Surowiecki described.
More concerning, it treated things like the EU’s value-added tax as a trade barrier, even though it applies to both domestic and foreign goods equally.
The result was a proposed 20% tariff justified by a formula that ignored the EU’s actual trade-weighted tariff average of just 2.7%, as reported by the World Trade Organization.
Capital Gains Debate
Ackman also weighed in on another hot-button issue—capital gains taxes.
After a post claimed Trump planned to eliminate the capital gains tax in 2025, Ackman confirmed the direction but offered a sharp critique: “Correction, we are on track to eliminate capital gains in 2025. There are better approaches to reducing taxes than wiping out gains.”
Personal Shots and Sharp Comebacks
As Ackman became more vocal, users on X pushed back. One joked that he’d be working in a Nike factory after Trump bankrupted him.
Ackman didn’t miss a beat: “Nice photo,” he replied.
Another post accused Ackman of protecting stockholder interests over everyday Americans, saying, “I just figured out why you’re having a temper tantrum… your firm is heavily long US stocks.” Ackman clapped back: “Yes. I am proudly long America.”
A Conflict of Interest?
Ackman raised concerns about Howard Lutnick, Secretary of Commerce, too. “I just figured out why Howard Lutnick is indifferent to the stock market and the economy crashing. He and Cantor are long bonds. He profits when our economy implodes.”
“It’s a bad idea to pick a Secretary of Commerce whose firm is levered long fixed income. It’s an irreconcilable conflict of interest.”
When a user accused him of hypocrisy for being long on stocks, Ackman responded, “No. I am long America and he is short. I am aligned with our country and our economy and he is short.”
Mixed Public Reaction
Some users backed Trump’s tariffs as a necessary reset for trade, arguing they will reduce imports and force other countries to the negotiating table.
Others accused Ackman of acting in his own financial interest or bringing up past controversies from the pandemic era.
Despite the backlash, Ackman stood firm.
“If you haven’t noticed by now, I speak the truth regardless of the consequences to me personally or what other people think,” he wrote.
As the April 9 deadline approaches, all eyes are on the White House and whether Trump’s advisors will revise the tariff formula—or double down on what Ackman calls “bad math.”