Citation Rates

A citation rate is the average number of citations received by a group of papers published in one research field in a given year. It is calculated by dividing the total number of citations received by all papers in the group (defined by research field and publication year) by the total number of papers in the group. The citation rate for all years is the total number of citations received by all papers in all fields published during the 10-year period divided by the total number of papers.

The time period for citation counts is 10 years, plus partial year counts for the current year (data is updated six times a year). Any paper published in the 10-year period may be cited by any other paper published during the same period. 

The citation rate in any single year can serve as a baseline to assess the impact of a paper in the same research field published in that year. Another baseline measure is the all-years citation rate, which is the citation rate for a 10-year period. It is important to recognize that citation counts grow over time. Typically, the citation rate of papers published in the last three years will be below the citation rate for all years.

Citation frequency is highly skewed, with many infrequently cited papers and relatively few highly cited papers. Consequently, citation rates should not be interpreted as representing the central tendency of the distribution.

Keep in mind that citation rates are calculated from the citation counts of papers that meet the criteria for inclusion in Essential Science Indicators. It is reasonable to infer that these rates are higher than those for all papers in a field, but the margin of difference is impossible to determine.

Sample Report

The following excerpt from a Citation Rates table reveals that on average, a paper from a Geosciences research field published in 2008 received 9.55 citations, and a paper from an Immunology research field published in 2008 received 20.42 citations. Those citations are from articles published between 2008 and the present. The report does not reveal how many citations are from any single year between 2008 and the present. The 10-year average for Geosciences papers is 9.54, and for Immunology papers it is 20.38. The 10-year averages are calculated from citations from articles published during the same 10-year period.

FIELD

2008

2009

2010

2011

2012

2013

ALL YEARS

GEOSCIENCES

9.55

7.68

5.11

2.82

0.72

0.12

9.54

IMMUNOLOGY

20.42

10.06

10.51

5.55

1.29

0.11

20.38