The Relative Citation Ratio (RCR) is a citation-based measure of scientific influence of a publication. It is calculated by the National Institutes of Health (NIH) in the United States as the citations of a paper, normalized to the citations received by NIH-funded publications in the same area of research and year.
The area of research is defined by the corpus of publications co-cited with the article of interest (the “co-citation network”) - it is therefore dynamically defined. In other words, the RCR indicates how a publication has been cited relative to other publications in its co-citation network and this is assumed to be reflective of the article’s area of research.
The RCR is calculated for all PubMed publications which are at least 2 years old. Values are centered around 1.0 so that a publication with an RCR of 1.0 has received the same number of citations as would be expected based on the NIH-norm, while a paper with an RCR of 2.0 has received twice as many citations as expected.
If you would like to see a detailed description of how the RCR is calculated, you can find this in the original publication. Another good overview of how the RCR works can be found here.
The RCR is made available in the NIH's Office of Portfolio Analysis's iCite database, with monthly snapshots posted on NIH's figshare platform. Once available, the latest snapshots are imported into Dimensions and displayed for all applicable publications (note that, because this is an externally calculated indicator, there may be discrepancies when trying to calculate the RCR based on Dimensions' own citation data vs. the NIH's.
RCR Mean / Mean per Year
RCR Mean is the arithmetic mean Relative Citation Ratio (RCR), which indicates the relative citation performance of an article when compared to other articles in its area of research. The values per year are the years in which the publications were published.
If a publication of "average" influence is supposed to have an RCR score of 1.0, what does this mean for a score of 2 versus a score of 5 for example?
An RCR score of 2 indicates the article is roughly twice as influential (through citations) as the average article, and a score of 5 is roughly five times as influential as the average. However, due to the complexity of truly identifying the "middle point" average of articles RCR scores, it is more advisable to take these as general indicators of comparative influence rather than exact figures.
How is the RCR different from the FCR?
The RCR is only calculated for articles which are found within PubMed, using the co-citation network to compare the article against. The FCR is calculated for all articles where a Field of Research (FoR) code is assigned, and uses other articles with the same FOR code to compare against, instead of the co-citation network used with the RCR. Both the RCR and FCR are only calculated for articles that are at least 2 years old.