Skip to Main Content

Bibliometrics: Citation Metrics

Citation Metrics

Citation metrics are used to help determine the relative quality and impact of a single article or the research output of an individual, group or institution using citation counts.

Citation metrics include:

 - Citation Rate

 - Citations Received Per Year

 - Mean Citation Rate

 - Median Citation Rate


H-Index is a metric calculated using publication and citation rates and can help determine relative quality of an author's work based on both productivity and impact. An author's h-index is equal to the number of papers that author has published (n) that have received at least n citations; if an author has published 32 papers and 5 of those papers have received at least 5 citations, the author has an h-index of 5.

Keep in mind that h-index cannot be compared across fields due to variations in citation conventions and habits and is inherently biased towards older authors who have not only published more works but had the time to accumulate more citations.

Analysis of Citing Articles

Performing a publication analysis on the publications that cite a given article or set of articles can provide insight into how articles are being used by the greater scientific community. Tools like Web of Science make performing such an analysis relatively simple and adds helpful context.

Percentile Ranks

An article's percentile rank is calculated based on how it compares to other papers published in the same year in the same field based on citation counts. In Web of Science, an article that received that received enough citations to rank it in the top one percent of papers published in the same year and field is considered a Highly Cited Paper. Percentile Ranks can be calculated for individual publications or for the output of an entire program or organization and have the advantage of being useful to compare impact across fields of study.

NOTE: Articles require at least 2 years to accumulate enough citations for article-level bibliometric indicators to be reliable.

This figure shows the H-Index of papers authored by NOAA's Office of Ocean Exploration.

“A scientist has index h if h of his/her Np papers have at least h citations each, and the other (Np-h) papers have no more than h citations each.” Hirsch, J.E. (2005) An index to quantify an individual's scientific research output. Proc Natl Acad Sci USA, 102(46), 16569-16572. doi:10.1073/pnas.0507655102.