Depending on the type of bosses you've had over the years, you might assume that performance review appraisal scores tend to have a more positive bias. The Harvard Business Review did some research and found they're more negative than you probably think.
Looking through six years of performance appraisal data, researchers found opposing evidence for a number of myths many of us might believe. The big one was just how much scores vary across people:
In fact, we found that appraisal scores did in fact vary quite a bit across individuals. Yes, there was an upward bias -- the average employee was rated slightly above "average" on the appraisal scale -- but the shape of the distribution looked surprisingly normal (measured via kernel density, a statistical technique for plotting data that smooths out irregularities). There were actually slightly more "poor" scores (the lowest rating) than "excellent" scores (the highest).
Which is all to say that, if you've even received a really bad performance review, it might be more common than you think. Heck, those excellent scores are even more rare, so go ahead and pat yourself on the back for that one too. This is all based on data from one company, so take it with a grain of salt, but it's still interesting. Head over to Harvard Business Review for a few more myths and a breakdown of their findings.
The Common Myths About Performance Reviews, Debunked [Harvard Business Review]