Unwelcome employee turnover can create big problems for managers, teams, and organizations, so it's important to understand the real drivers of attrition. New research from Ethan Bernstein, associate professor at Harvard Business School, and Michael Horn, cofounder of the Clayton Christensen Institute, points to a host of push and pull forces that cause workers to jump ship and also outlines better retention strategies. They are the coauthors, along with Bob Moesta, of the HBR article "Why Employees Quit" and the book Job Moves: 9 Steps for Making Progress in Your Career.