Field normalized citation rate
The field normalized citation rate is widely used for research evaluation. It is a publications number of citations compared to the average number of citations for similar publications.
Since the publication patterns differ between research fields, raw citation counts should not be compared between fields in research evaluations. The field normalized citation rate is one way to deal with this problem. It is used in the THE Ranking, in the swedish research funding allocation system, in the KTH internal allocation system, in the KTH RAE and in the yearly indicator report.
The average field normalized citation rate is calculated by dividing the number of citations for a publication with the average number of citations for publications of the same type, published the same year and published in journals categorized as belonging to the same research area (see picture below). Hence, the average field normalized citation rate is 1 and a value of e.g. 1.50 indicates that a publication have been cited 50 percent more than the average. The field normalized citation rate can also be calculated as an average of a set of publication, e.g. publications published by a research group, a journal or a country.
One should bear in mind that even though the field normalized citation rate is compensating for different publication and citation patterns there can still be biases in the results, since the research areas are covered in different extent in the databases used for the analysis.