Average citation rates by field 1998-2008

SOURCE: Thomson Reuters’ Essential Science Indicators database, 1 January 1998-31 October 2008

Too often, journal impact factors serve as proxies for the influence of individual research papers. Journal impact factors express the average number of times a journal’s papers have been cited in the recent past, but they often overestimate the influence of a paper. But even if one obtains the actual number of citations, the question remains: “What does that number indicate?”

Fields 19981999 200020012002200320042005200620072008All years
All fields17.4716.8116.0414.7013.1611.199.286.864.211.900.329.70
Agricultural sciences10.9610.8410.789.658.647.686.214.432.721.080.186.06
Clinical medicine20.3219.7118.8117.4915.9413.9011.578.725.352.360.3611.76
Computer science7.066.305.705.865.793.672.531.850.930.630.103.06
Economics and business10.199.228.517.437.125.804.573.081.660.670.135.02
Materials science9.429.219.338.667.677.095.814.282.711.180.175.56
Molecular biology46.0643.7641.2337.6933.28.7222.6916.4510.254.600.7524.75
Plant and animal science12.5912.0411.4810.419.257.866.524.622.791.200.226.90
Social sciences7.487.186.896.135.624.804.072.991.720.690.164.06
Space science21.0722.8017.8119.2815.0415.3112.5010.176.793.830.6612.91

The data in the table above clarify matters in two ways. Different fields of investigation exhibit widely different average rates of citation, and publication year affects the score, because older papers have had more time to attract citations. The field with the highest average citation rate is molecular biology and genetics, while that with the lowest average is mathematics, according to data from Thomson Reuters’ Essential Science Indicators database, 1998-2008. Of course, field definitions matter, and in this case groups of journals serve to define subject categories; in addition, individual articles in multidisciplinary journals are assigned to specific fields. One might think that the number of papers published or the population of researchers in a field are the predominant factors that influence the average rate of citation, but it is mostly the average number of references presented in papers of the field that determines the average citation rate. Mathematics papers typically list few references, whereas those in molecular biology display extensive citations.

Time matters, too. Naturally, more recent papers have lower averages. The only reasonable use of journal impact factors as proxy measures for individual papers is when papers have not had time to collect citations; in these cases, the journal gives some indication about the probable impact of a paper because journals with high impact factors in their field typically have more stringent review standards than those with lower impact factors. Still, do-it-yourself citation analysts are urged to focus on the number of citations a paper has collected and to weigh that number by the average citation rate for papers in the same field and the same year of publication. Finally, the type of paper is relevant. The statistics above are limited to articles in journals indexed by Thomson Reuters. Other types of articles such as editorials, correction notices and meeting abstracts exhibit lower citation averages.

See Henk F. Moed, Citation Analysis in Research Evaluation, Springer, 2005, and Joint Committee on Quantitative Assessment of Research, Citation Statistics: A Report from the International Mathematical Union (IMU) in co-operation with the International Council of Industrial and Applied Mathematics (ICIAM) and the Institute of Mathematical Statistics (IMS), June 2008 (www.mathunion.org/fileadmin/IMU/Report/CitationStatistics.pdf)

Already registered?

Sign in now if you are already registered or a current subscriber. Or subscribe for unrestricted access to our digital editions and iPad and iPhone app.

Featured Jobs

Academic Partnership Manager LONDON SOUTH BANK UNIVERSITY

Register to continue  

You've enjoyed reading five THE articles this month. Register now to get five more, or subscribe for unrestricted access.

Most Commented

Universities to scale back liberal arts and social science courses

  • David Humphries illustration (24 September 2015)

A Russell Group tagline rap is further proof that we need to reform the academy’s approach, argues Philip Moriarty

  • World University Rankings

US continues to lose its grip as institutions in Europe up their game

  • World University Rankings 2015-2016 methodology

Change for the better: fuelled by more comprehensive data, the 2015-2016 rankings probe deeper than ever

Inspired by previous movement in 1960s, PhD students say that ‘science is not neutral’ and urge scientists to confront their assumptions