Performance appraisals are one of the most ubiquitous, and also one of the most unpopular, protocols in workplace. In fact, several companies have recently made headlines in their attempts to go about them differently. But amid these changes, how many organizations have ever taken a close look at how performance reviews actually operate in their own workplace, over the long term? My colleague Martin Conyon and I recently had the opportunity to take a deep dive to do just this, analyzing the performance appraisal data from a large U.S. corporation between 2001 and 2007. We looked at all of the scores and associated employment outcomes over these years, and what we found punctures many of the myths about performance reviews that have developed over time.