Pershing Square Capital sees an undervalued stock that has strong growth potential in China. : Starbucks stock rose as much as 5% Tuesday after Pershing Square Capital Management, a hedge fund led by activist investor Bill Ackman, disclosed a stake in the coffeeshop chain. The investment—which Ackman announced during a presentation at a New York investment conference—involves a stake worth $900 million. Ackman’s presentation said that Starbucks’ return including dividends is flat over three years, but that its forward price-to-earnings ratio of 22 is at a “substantial discount” to its historical average.