Jamie Dimon might run America's largest bank, but he's focused on assigning the firm's biggest competitive battles to small teams. In his annual letter to shareholders , Dimon, who has been JPMorgan's CEO since 2006, shared a range of management lessons he's learned, from organizing effective teams to creating company culture. Though JPMorgan employs some 320,000 people, Dimon said said that "the real competitive battles" are waged by small, laser-focused teams . The idea, he explained, is that