His Pershing Square Capital Management owns 10 stocks.Over the years, the billionaire Bill Ackman has become one of the big investors to watch. Ackman runs Pershing Square Capital Management, the investment manager for Pershing Square Holdings. The fund generated a gain of 12.7% this year through July, ahead of the broader market, and is up 23.4% over the past year.Pershing typically invests in eight to 12 publicly traded stocks at any one time and held about $13.7 billion in publicly traded stocks at the e ...