A tweet posted by Donald Trump has made Pfizer shares collapse. Today Mr. Trump has written: “Pfizer & others should be ashamed that they have raised drug prices for no reason. They are merely taking advantage of the poor & others unable to defend themselves, while at the same time giving bargain basement prices to other countries in Europe & elsewhere. We will respond!” and the company’s shares have immediately dropped. Trump’s tweet comes after the recently spread news of Pfizer increasing 40 drug prices by 8%, notwithstanding Trump’s request that the pharmaceutical companies voluntarily lower drug prices.