Volkswagen stock has been heavily shorted. This means traders borrowed shares, sold them, expecting to buy them back at a cheaper price and pocket the profit. It closed at about 200 on Friday.
Over the weekend, Porsche they would increase their share of Volkswagen stock to 75%. The stock exploded upwards, closing today at over 900. Reports said some hedge fund traders were in tears.
The math. You short 100 shares at 200 and pocket 20,000. The stock goes to 900. You are out 70,000 ((200*100) – (900*100)) and will have almost certainly gotten a margin call to either make up the difference in cash in the account by the end of day or margin clerks will buy back the stock at the market and you take the loss. That’s why (some) traders were in tears…