Shares of Herbalife Corporation (HLF) rose sharply in trading on Friday after the company announced that it will buy back roughly seven percent of its stock. The buyback is designed to improve shareholder value. The move comes as yet another blow to activist investor Bill Ackman, who has maintained a short position in HLF since 2012. Shares of HLF closed at 75.25, up +11.28% for the session. Keep an eye on HLF for further developments.