Social Comparison theory is important when thinking about how leaders evaluate staff. One of the significant challenges.... leaders experience when completing performance reviews is that they are actually comparing themselves and their performance to their employee's performance. In areas where they experience their employee doing a better job than themselves, they are likely to rate that behavior high and vice versa.
It is nearly impossible to defeat this natural bias. Being conscious of this bias....is the first step.
Please take a moment to learn more about Social Comparison Theory from Fast Company.