These days everyone knows that finding a mentor is valuable. But it’s increasingly rare that we actually have one. In an in-depth study of professional service firms, Harvard Business School professor Thomas DeLong and his colleagues discovered: “Everyone we spoke with over age 40 could name a mentor in his or her professional life, but younger people often could not.” They note, “Junior professionals joining a firm 20 years ago could count on the partners treating them like protégés.” Today job turnover, layoffs, and increased bottom-line pressures have taken a hatchet to that “implicit agreement.” The answer isn’t to give up on finding a mentor, however — it’s to broaden our search.