The Relative Citation Ratio (RCR) is a citation-based measure of scientific influence of a publication. It is calculated 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.

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.