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What a Trump tweet means for the stock market

In the following post, D’Amore-McKim School of Business Professor Jeffery Born answers questions about his recent research that examines the impact that tweets from President Donald Trump have on a Semi-Strong Form (SSF) Efficient Market.


August 3, 2017

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Q: Which tweets by Trump did you investigate?

We focused on tweets by President Donald Trump, which mentioned publicly traded firms (n=10) from the date of his election on November 8, 2016, to his inauguration on January 20, 2017. Fifteen tweets were separated by enough time for the stock market’s response to the information to be considered independent.

Q: Why did you look at these events?

In real time, there were many in the press who reported that the President-elect’s tweets were driving the firm’s stock price in a significant fashion. None of the press reports contrasted these movements against the same day movement in broad market averages, nor did the press report how risky the firms were (compared to the broad market). Failing to control for movements in the broad market and risk limits the conclusions one can draw the firm responses.

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