Proposal of using scaling for calculating field-normalized citation scores

Since the end of the 1980s, citation impact values –especially for evaluative purposes– are increasingly presented as fieldnormalized citation scores than as bare citation counts or citation rates. In rather popular variants of the scores, the average score over a publication year is not exactly one due to multiple Web of Science subject categories per paper. We propose a scaling method which introduces slight changes in the field-normalized scores of each paper that ensures that the average value of all scores equals one.