For marketers, understanding what drives consumers is vital in good and bad economic times.  Harvard Business School professor John Quelch recommends "segmentation": breaking out consumers into different groups based on their behavior.  Given the severity of the current recession, he says segmentation exercises that marketers have done in the past are "obselete," and "most companies need to go and re-talk to their customers and reframe their segmentation approach."   Quelch and Katherine Jocz break consumers into four groups: The "Slam-on-the-brakes segment, the Pained-but-patient, the Comfortably well-off, and the Live-for-today segment."  They explain the psychology of each consumer segment in their article, How to Market in a Downturn.  It is the cover story for the April edition of Harvard Business Review.  Read it here and watch Quelch explain this consumer segmentation below.