Field Weighted Citation Impact
Can apply to: Primarily journal articles, but also other kinds of research outputs, such as book chapters and conference proceedings that are sufficiently covered by abstract and citation databases.
Metric definition: The Field-Weighted Citation Impact (FWCI) is the ratio between the actual citations received by set of publications and the average number of citations received by all other similar publications. The latter is referred to as the expected number of citations. Similar publications are ones in the same discipline, of the same type, and of the same age. The FWCI is a Snowball Metric, a set of standardized research metrics developed through a academic-industry collaboration.
Metric calculation: The FWCI is measured by dividing the number of citations a publication received by the average number of citations to publications in a database published in the same year, of the same type, and within the same subject category. When multiple publications are being considered, the ratio between the actual and average citations for each publication are calculated first. The FWCI is the mean result. Publications can also be assigned to more than one subject category. In these cases, the publication and its citation counts are equally distributed across the relevant subject categories.
Data sources: The FWCI is dependent on citation and indexing information available in abstract and citation databases, such as Scopus and World of Science. In addition to citation counts, these sources classify publications by year, type, and subject. Scopus, for example, uses the All Science Journal Classification (ASJC) schema to categorize publications by subject, and the assignments are publication driven.
Appropriate use cases: The FWCI was conceived to facilitate the benchmarking of citation performance across groups of different size, disciplinary scope, and age, such as research large groups, institutions, or geographic regions. It is meant to correct for the dominant effect disciplinary patterns of scholarly communication and publication age can have on non-weighted metrics, such as citation counts. The global mean of the FWCI is 1.0, so it is easy to compare a set of values to a benchmark. For example, an FWCI of 1.50 means 50% more cited than the world average; whereas, an FWCI of .75 means .25% less cited than the world average.
Limitations: The FWCI uses a mean value, which can be strongly influenced by outliers. The distribution of citations across publications is often highly skewed. Most publication in a sample will receive minimal citation attention, except for a small numbers of exceptions. Outliers will have a heavier influence on smaller samples, and result in a more unstable FWCI. Additionally, the FWCI is limited to citation data from the year of publication, plus 3 years, which could disadvantage content with longer citation timeframes.
Inappropriate use cases: Like citation counts, citation based metrics should not be interpreted as a direct measure of quality.
Available metric sources: Article level FWCI values are available in Scopus, entity level (e.g. researcher, research group, institution, etc.) FWCI values are available in SciVal. It should also be noted that other metrics sources provide similarly calculated field-weighted, citation based metrics.
Transparency: The FWCI’s calculation is described in the Snowball Metrics Recipe Book, and the SciVal Metrics Guidebook. The FWCI is dependent upon a publication’s classification by discipline, publication type, and year. While the year and type of publication are recorded and verifiable, discipline assignments are not.
Timeframe: The FWCI uses citation data from the year of publication, plus 3 years.