Here’s What a Trump Tweet Does to a Company’s Share Price

Feb 24, 2017

President Donald Trump's Twitter rants on a variety of topics have become almost legendary, and among his favorite targets are companies that he believes are not doing what they should be, whether it's aircraft manufacturers like Boeing or automakers like Ford.

In almost every case, when the president unleashes his Twitter (twtr) fury, the share price of the affected company drops—in some cases fairly significantly. Lockheed Martin's stock (lmt), for example, plunged by more than 5% in December, after Trump criticized the company by saying the cost of its F-35 jet aircraft contract was "out of control."

But do these negative effects last, or are they relatively fleeting? Some research from the Wall Street Journal shows that it's mostly the latter.

The Journal created a "Trump Target Index" of 12 stocks that have been affected by Trump's tweets over the past year, and then tracked what has happened to their share prices since he mentioned them on Twitter. Overall, the index is up by 32.5%, outperforming both the Dow Jones Industrial Average and the Standard & Poor's 500 index.

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In many cases, shares of companies that Trump has criticized rebounded from their losses on the same day he mentioned them. (A Reuters survey found something similar recently.) Lockheed Martin dropped by more than 5% after he slammed the company's jet program, but by the end of the day they were only down by about 2.5%.

Related: The Impact of Trump Tweets on Company Shares Is Mostly Short Lived

Even Nordstrom (jwn), which Trump attacked just a few weeks ago after the company removed his daughter Ivanka's fashion designs from their stores, has increased in value since the attack.

It should be noted that the Journal's index is distorted to some extent by the fact that the Trump target group includes Apple, which Trump criticized in January 2016 for not helping investigators unlock the iPhone of the suspect in the San Bernardino shootings. The Journal says its index is equal-weighted, which means Apple's massive market value of $700 billion or so shouldn't have affected the overall performance of the group. But shares of the company (aapl) have climbed by more than 40% in the past year, and that rise likely accounts for a large part of the index's improvement over that period.

It's also worth noting that the stock market as a whole has climbed in value by more than 25% over the past year, depending on which index you look at. While the Trump target group outperformed the Dow and the S&P 500, it didn't do so by very much. In the case of the Dow, the Trump index is only higher by a couple of percentage points.

In any case, according to the Journal's research, almost every one of the stocks mentioned by Trump have risen in value. The only exception is Toyota (tm), which has declined in value by more than 5%, losing about $12 billion in market value. Trump criticized the company for planning to build a new car plant in Mexico instead of the United States.

Both Apple and Toyota are good examples—from either end of the spectrum—that macro-economic and company-specific factors will almost always have much more impact on the fate of a company's share price than a tweet, even when it comes from the president.

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