I've never been a fan of employee ranking. There is little evidence to prove that it drives sustainable positive behavior. In the past I would have argued that Sales might be an exception to this rule, however, in this article for the New York times, Phyllis Korkki presents evidence that even Sales responds unfavorably to ranking.
Professor Barankay found that the sales representatives who did not know how they ranked achieved higher subsequent sales than those who were aware of their comparative ranking. The results of the workers who had received high rankings neither improved nor worsened.1