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A phone screen displays the Truth Social app in Washington, DC, on February 21, 2022.
CNN  — 

President-elect Donald Trump’s social media stock had been sinking fast after a short-lived, post-election-victory surge this week. Then, with a single post on Truth Social, he helped boost the stock again – and added a half billion dollars to his net worth as a result.

At Friday’s market open, in what was likely a classic “buy the rumor and sell the news” trade, shares of Trump Media and Technology Group had fallen 42% since their recent peak shortly after Wednesday’s open. Traders often buy a stock in anticipation of a positive event for a company – and when it happens, they sell to take their share of their profitable bet.

But then, a half-hour into trading Friday, when shares were down again, Trump sent out a Truth Social post about the company’s stock: “There are fake, untrue, and probably illegal rumors and/or statements made by, perhaps, market manipulators or short sellers, that I am interested in selling shares of Truth. THOSE RUMORS OR STATEMENTS ARE FALSE. I HAVE NO INTENTION OF SELLING!”

Immediately after, the stock surged, rising nearly 15% Friday. Trump is the company’s single largest shareholder, and his 114.75 million shares are now worth about $3.7 billion. That’s up from $3.2 billion at Friday’s market open.

Friday’s jump helped the stock land in the green for the week – but not by much. Trump media rose just 4.4% over the past five days.

The company has been called a “meme stock” that has been extremely volatile since it went public in March, and it does not trade on its fundamental business value. Throughout the year, Trump Media’s stock has traded as a kind of barometer for Trump’s election chances. It quadrupled in value over a five-week span before plunging by 41% over three days at the end of last week. It then rebounded sharply the day before the election.

Truth Social’s business is minuscule by comparison with its better-known rivals such as X, TikTok and Instagram. The company is in a cash crunch and said it brought in less than $1 million in revenue in the past quarter.

Trump has previously said he has no intention to sell his shares in the stock. That could be difficult to do, anyway, because the company’s valuation depends almost entirely on Trump’s ownership and participation on Truth Social, its core product. But Friday’s reminder was enough to give traders hope that Trump will continue with the company, even while he is President of the United States.

The fact that Trump can benefit financially from the statements he makes on the social media platform has raised ethical concerns – as have his many other business ties.