A distinctive brand is good for business, of course. But you’d be surprised how important it is to a firm’s overall performance. We studied how customer perceptions of brand differentiation related to stock price over the course of 11 years in 275 “monobrand” companies such as AT&T, Krispy Kreme Doughnuts, and Reebok. (Customer brand-perceptions data came from Y&R’s Brand Asset Valuator survey.)