Citation averages, 2000-2010, by fields and years

The table above provides average rates of citation by field for journal articles indexed by Thomson Reuters in its Essential Science Indicators database from 2000 to 2010. The statistics provided in ESI are restricted to items coded as regular articles and reviews. The columns represent the publication year of the journal articles while the rows designate broad field areas, defined by sets of journal. In ESI, papers in multidisciplinary journals are selectively assigned to their appropriate fields. The citation counts used to calculate these averages are from the year of publication to the end of 2010. Thus, older papers have had more time to collect citations than newer ones and show higher values. As one reads the chart from left to right, therefore, the citation averages decline. The righthand column provides the field average based on 2000-2010 papers cited over the entire 11-year period. Typically, the 11-year average is approximately half that for papers from 2000 cited from that year to 2010. The fields are ranked by the 2000-10 citation averages.

Citation rates are chiefly determined by the average number of references made in articles in a field, rather than the size of the field or how “hot” it may be. The rank order of the fields has been constant for many years. Molecular biology and genetics, immunology and neuroscience are the areas with the highest average citation rates, whereas computer sciences and mathematics exhibit the lowest averages.

In analysing the research impact of individuals and their papers, the number of citations earned should be compared with baseline measures. Journal impact factors should not be used in evaluating the influence of papers or people, since they are short-term measures of average influence for entire journals: their use as proxies for baselines, although widespread, is misguided and should be recognised as bad bibliometric practice.

Evaluating the influence of individual papers and collections of papers for a researcher or research group should, Thomson Reuters recommends, go beyond the use of the statistics above, which are meant to simply illustrate the significant differences in citation averages among fields. The data according to broad fields are, after all, averages built from a wide range of values for individual journals and their papers. A good procedure would be to employ as a baseline for each paper examined the average for papers of the same year, published in the same journal and of the same article type.

The data above update a similar table published in these pages two years ago. See: http://tinyurl.com/5w6czns

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