Citation metrics for appraising scientists: misuse, gaming and proper use

Citation and other metrics are widely misused, but when properly used, they can be valuable. Science itself thrives on quantitative measurement. Quantitative indicators aim to provide objective data instead of biased beliefs. Here, we focus on citation metrics in appraising scientists1 for hiring, promotion, tenure, funding, selection for some award, recognition or bonus, or other reasons. Many tricks exist to game citation metrics (Box); however, proper use of metrics may overcome these deficiencies. Generic challenges that we describe here may partly apply also to larger, more composite entities such as the appraisal of journals, institutions or large research portfolios, for example, at a national level.