Bibliometrics

Bibliometric Analysis of Papers on Topics Related to Safe Pesticides/Safe Products
November 15, 2006

This is a bibliometric analysis of the papers prepared by intramural and extramural researchers of the U.S. Environmental Protection Agency (EPA) on topics related to safe pesticides/safe products (SP/SP). For this analysis, 261 papers published from 1998 to 2005 were reviewed. These publications were cited 2,491 times in the journals covered by Thomson’s Web of Science.¹ Of these 261 publications, 216 (83%) have been cited at least once in a journal.

Searches of Thomson’s Web of Science and Scopus² were conducted to obtain times cited data for the safe pesticides/safe products journal publications. The analysis was completed using Thomson’s Essential Science Indicators (ESI) and Journal Citation Reports (JCR) as benchmarks. ESI provides access to a unique and comprehensive compilation of essential science performance statistics and science trends data derived from Thomson’s databases. For influence and impact measures, ESI employs both total citation counts by field and cites per paper scores. The former reveals gross influence while the latter shows weighted influence, also called impact. JCR is a recognized authority for evaluating journals. It presents quantifiable statistical data that provide a systematic, objective way to evaluate the world’s leading journals and their impact and influence in the global research community. The two key measures used in this analysis to assess the journals in which the EPA safe pesticides/safe products papers are published are the Immediacy Index and the Impact Factor. The Immediacy Index is a measure of how quickly the “average article” in a journal is cited. This index indicates how often articles published in a journal are cited within the same year and it is useful in comparing how quickly journals are cited. The Impact Factor is a measure of the frequency with which the “average article” in a journal has been cited in a particular year. The Impact Factor helps evaluate a journal’s relative importance, especially when compared to other journals in the same field.

Highly Cited Safe Pesticides/Safe Products Publications

The 261 safe pesticides/safe products papers reviewed for this analysis covered 16 of the 22 ESI fields. The distribution of the papers among these 16 fields and the number of citations by field are presented in Table 1.

Table 1. Safe Pesticides/Safe Products Papers by ESI Fields

There are 58 (22.2% of the papers analyzed) highly cited EPA safe pesticides/safe products papers in 12 of the 16 fields—Environment/Ecology, Pharmacology & Toxicology, Microbiology, Computer Science, Biology & Biochemistry, Plant & Animal Science, Engineering, Neuroscience & Behavior, Economics & Business, Chemistry, Multidisciplinary, and Agricultural Sciences—when using the ESI criteria for the top 10% of papers. Table 2 shows the number of EPA papers in those 12 fields that meet the top 10% threshold in ESI. Six (2.3%) of the papers analyzed qualify as highly cited when using the ESI criteria for the top 1% of papers. These papers cover two fields—Environment/ Ecology and Computer Science. Table 3 shows the 6 papers by field that meet the top 1% threshold in ESI, and the citations for these papers are provided in Tables 4 and 5. There were no papers that meet the top 0.1% threshold or the top 0.01% threshold in ESI.

Table 2. Number of Highly Cited Safe Pesticides/Safe Products Papers by Field (top 10%)

Table 3. Number of Highly Cited Safe Pesticides/Safe Products Papers by Field (top 1%)

Table 4. Highly Cited Safe Pesticides/Safe Products Papers in the Field of Environment/Ecology (top 1%)

Table 5. Highly Cited Safe Pesticides/Safe Products Paper in the Field of Computer Science (top 1%)

Ratio of Actual Cites to Expected Citation Rates

The expected citation rate is the average number of cites that a paper published in the same journal in the same year and of the same document type (article, review, editorial, etc.) has received from the year of publication to the present. Using the ESI average citation rates for papers published by field as the benchmark, in 12 of the 16 fields in which the EPA safe pesticides/safe products papers were published, the ratio of actual to expected cites is greater than 1, indicating that the safe pesticides/safe products papers are more highly cited than the average papers in those fields (see Table 6).

Table 6. Ratio of Average Cites to Expected Cites for Safe Pesticides/Safe Products Papers by Field

JCR Benchmarks

Impact Factor. The JCR Impact Factor is a well known metric in citation analysis. It is a measure of the frequency with which the “average article” in a journal has been cited in a particular year. The Impact Factor helps evaluate a journal’s relative importance, especially when compared to others in the same field. The Impact Factor is calculated by dividing the number of citations in the current year to articles published in the 2 previous years by the total number of articles published in the 2 previous years.

Table 7 indicates the number of safe pesticides/safe products papers published in the top 10% of journals, based on the JCR Impact Factor. Ninety-two (92) of 261 papers are published in the top 10% of journals, representing 35% of EPA’s safe pesticides/safe products papers. This indicates that more than one-third of the safe pesticides/safe products papers are published in the highest quality journals as determined by the JCR impact factor, which is 3.5 times the expected percentage.

Table 7. Safe Pesticides/Safe Products Papers in Top 10% of Journals by JCR Impact Factor

Immediacy Index. The JCR Immediacy Index is a measure of how quickly the average article in a journal is cited. It indicates how often articles published in a journal are cited within the year they are published. The Immediacy Index is calculated by dividing the number of citations to articles published in a given year by the number of articles published in that year.

Table 8 indicates the number of safe pesticides/safe products papers published in the top 10% of journals, based on the JCR Immediacy Index. Sixty-five (65) of the 261 papers appear in the top 10% of journals, representing 25% of the safe pesticides/safe products papers. This indicates that one-quarter of the safe pesticides/safe products papers are published in the highest quality journals as determined by the JCR immediacy index, which is 2.5 times higher than the expected percentage.

Table 8. Safe Pesticides/Safe Products Papers in Top 10% of Journals by JCR Immediacy Index

Hot Papers

ESI establishes citation thresholds for hot papers, which are selected from the highly cited papers in different fields, but the time frame for citing and cited papers is much shorter—papers must be cited within 2 years of publication and the citations must occur in a 2-month time period. Papers are assigned to 2-month periods and thresholds are set for each period and field to select 0.1% of papers. There were no hot papers identified for the current 2-month period (i.e., January-February 2006), but there were a number of hot papers identified from previous periods.

Using the hot paper thresholds established by ESI as a benchmark, 3 hot papers, representing 1.2% of the safe pesticides/safe products papers, were identified in two fields—Environment/Ecology and Engineering. The hot papers are listed in Table 9.

Table 9. Hot Papers Identified Using ESI Thresholds

Author Self-Citation

Self-citations are journal article references to articles from that same author (i.e., the first author). Because higher author self-citation rates can inflate the number of citations, the author self-citation rate was calculated for the safe pesticides/safe products papers. Of the 2,491 total cites, 158 are author self-cites—a 6.3% author self-citation rate. Garfield and Sher³ found that authors working in research-based disciplines tend to cite themselves on the average of 20% of the time. MacRoberts and MacRoberts⁴ claim that approximately 10% to 30% of all the citations listed fall into the category of author self-citation. Kovacic and Misak⁵ recently reported a 20% author self-citation rate for medical literature. Therefore, the 6.3% self-cite rate for the safe pesticides/safe products papers is well below the range for author self-citation.

Highly Cited Researchers

A search of Thomson’s ISIHighlyCited.com revealed that 7 (1.1%) of the 653 authors of the safe pesticides/safe products papers are among the world’s most highly cited researchers. ISIHighlyCited.com is a database of the world’s most influential researchers who have made key contributions to science and technology during the period from 1981 to 1999. The highly cited researchers identified during this analysis of the safe pesticides/safe products publications are presented in Table 10.

Table 10. Highly Cited Researchers Authoring Safe Pesticides/Safe Products Publications

¹Thomson’s Web of Science provides access to current and retrospective multidisciplinary information from approximately 8,700 prestigious research journals from around the world. Web of Science also provides cited reference searching and navigates users to electronic full-text journal articles.

² Scopus is a large abstract and citation database of research literature and quality Web sources designed to support the literature research process. Scopus offers access to 15,000 titles from 4,000 different publishers, more than 12,850 academic journals (including coverage of 535 open access journals, 750 conference proceedings, and 600 trade publications), 27 million abstracts, 245 million references, 200 million scientific Web pages, and 13 million patent records.

³Garfield E, Sher IH. New factors in the evaluation of scientific literature through citation indexing. American Documentation 1963;18(July):195-210.

⁴ MacRoberts MH, MacRoberts BR. Problems of citation analysis: a critical review. Journal of the American Society of Information Science 1989;40(5):342-349.

⁵ Kavaci N, Misak A. Author self-citation in medical literature. Canadian Medical Association Journal 2004;170(13):1929-1930.

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