Bibliometrics

2005 Bibliometric Analysis (Revised) for Papers on Topics Related to Land/Remediation Research
November 2005 Report (RevisedJune 2007)

This is a revised bibliometric analysis of the papers prepared by intramural and extramural researchers of the U.S. Environmental Protection Agency (EPA) on topics related to land/remediation. This analysis was revised in June 2007 because the journals were initially categorized into the fields used by Thomson Scientifics Essential Science Indicators (ESI) using information provided in Thomsons Journal Citation Reports (JCR); for this revised analysis, the journals were categorized into ESI fields using the journal category list by ESI that is available on the Internet athttp://in-cites.com/journal-list/index.html. The Journal List for ESI was made available in 2006 and the current list contains all of the 12,734 journals covered for ESI up to December 31, 2006. This list is updated bimonthly by Thomson. This revised bibliometric analysis will allow comparison of the results of this 2005 analysis to those of the analysis performed in 2007.

This is a bibliometric analysis of the papers prepared by intramural and extramural researchers on topics related to land/remediation research. For this analysis, 1,141 papers were reviewed. These 1,141 papers, published from 1995 to 2005, were cited 14,477 times in the journals covered by Thomsons Web of Science.¹ Of these 1,141 papers, 1,030 (90.3%) have been cited at least once in a journal.

The analysis was completed using Thomson=s ESI and JCR as benchmarks. ESI provides access to a unique and comprehensive compilation of essential science performance statistics and science trends data derived from Thomsons databases. The chief indicators of output, or productivity, are journal article publication counts. For influence and impact measures, ESI employs both total citation counts and cites per paper scores. The former reveals gross influence while the latter shows weighted influence, also called impact. JCR presents quantifiable statistical data that provide a systematic, objective way to evaluate the worlds leading journals and their impact and influence in the global research community.

Summary of Analysis

Nearly one-fifth of the land/remediation publications are highly cited papers. A review of the citations indicates that 227 (19.9%) of the land/remediation papers qualify as highly cited when using the ESI criteria for the top 10% of highly cited publications. Fifteen (1.3%) of the land/remediation papers qualify as highly cited when using the criteria for the top 1%. One (0.1%) of these papers qualify as very highly cited (in the top 0.1%). None of the papers meet the highest threshold (the top 0.01%) for highly cited papers.

The land/remediation papers are more highly cited than the average paper. Using the ESI average citation rates for papers published by field as the benchmark, in 9 of the 16 fields in which the EPA land/remediation papers were published, the ratio of actual to expected cites is greater than 1, indicating that the land/remediation papers are more highly cited than the average papers in those fields.

Nearly one-quarter of the land/remediation papers are published in very high impact journals. Two hundred seventy-six (276) of 1,141 papers were published in the top 10% of journals ranked by JCR Impact Factor, representing 24.2% of EPAs land/remediation papers. Two-hundred forty-three (243) of the 1,141 papers appear in the top 10% of journals ranked by JCR Immediacy Index, representing 21.3% of EPA=s land/remediation papers.

Eleven of the land/remediation publications qualified as 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 shorterpapers must be cited within 2 years of publication and the citations must occur in a 2-month time period. Using the current hot paper thresholds established by ESI as a benchmark, 11 of the land/remediation papers, representing 1.0% of the land/remediation publications, were identified as hot papers in the analysis.

The authors of the land/remediation papers cite themselves less than the average self-citation rate. Seven hundred sixty-seven (767) of the 14,477 cites are author self-cites. This 5.3% author self-citation rate is well below the accepted range of 10-30% author self-citation rate.

Highly Cited Land/Remediation Publications

The 1,141 land/remediation papers reviewed for this analysis covered 16 of the 22 ESI fields of research. The distribution of the papers among these 16 fields and the number of citations by field are presented in Table 1.

Table 1. Land/Remediation Papers by ESI Fields

There were 227 (19.89% of the papers analyzed) highly cited EPA land/remediation papers in 12 of the 16 fieldsEnvironment/Ecology, Engineering, Chemistry, Microbiology, Pharmacology & Toxicology, Plant & Animal Science, Physics, Biology & Biochemistry, Geosciences, Materials Science, Agricultural Sciences, and Multidisciplinarywhen using the ESI criteria for the top 10% of papers. Table 2 shows the number of EPA papers in those 12 fields that met the top 10% threshold in ESI.

Fifteen (1.31%) of the papers analyzed qualified as highly cited when using the ESI criteria for the top 1% of papers. These papers were categorized in six fieldsEnvironment/Ecology, Chemistry, Microbiology, Engineering, Pharmacology & Toxicology, and Materials Science. Table 3 shows the 15 papers by field that met the top 1% threshold in ESI. There was one (0.09% of the papers analyzed) very highly cited EPA land/remediation papers in one field Pharmacology & Toxicology. This one paper met the top 0.1% threshold in ESI. None of the land/remediation papers met the highest threshold for highly cited papers (i.e., the top 0.01% threshold) in ESI., which is not surprising given that the expected number of papers that would meet this threshold is 0.11.

Table 2. Number of Highly Cited Land/Remediation Papers by Field (top 10%)

Table 3. Number of Highly Cited Land/Remediation Papers by Field (top 1%)

The citations for the highly cited papers in the top 1% are presented in Tables 4 through 9. The citations for the very highly cited papers are listed in Table 10.

Table 4. Highly Cited Land/Remediation Papers in the Field of Environment/Ecology (top 1%)

Table 5. Highly Cited Land/Remediation Papers in the Field of Chemistry (top 1%)

Table 6. Highly Cited Land/Remediation Papers in the Field of Microbiology (top 1%)

Table 7. Highly Cited Land/Remediation Papers in the Field of Engineering (top 1%)

Table 8. Highly Cited Land/Remediation Papers in the Field of Pharmacology & Toxicology (top 1%)

Table 9. Highly Cited Land/Remediation Papers in the Field of Materials Science (top 1%)

Table 10. Very Highly Cited Land/Remediation Papers (Top 0.1%)

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 9 of the 16 fields in which the EPA land/remediation papers were published, the ratio of actual to expected cites is greater than 1, indicating that the EPA papers are more highly cited than the average papers in those fields (see Table 11).

Table 11. Ratio of Average Cites to Expected Cites for Land/Remediation Papers by Field

JCR Benchmarks

The 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 journals 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 12 indicates the number of land/remediation papers published in the top 10% of journals, based on the JCR Impact Factor. Two hundred seventy-six (276) of 1,141 papers were published in the top 10% of journals, representing 24.2% of EPAs land/remediation papers.

Table 12. Land/Remediation Papers in Top 10% of Journals by JCR Impact Factor

Immediacy Index

The journal 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 13 indicates the number of EPA papers published in the top 10% of journals, based on the JCR Immediacy Index. Two hundred forty-three (243) of the 1,141 papers appear in the top 10% of journals, representing 21.3% of EPAs land/remediation papers.

Table 13. Land/Remediation 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 shorterpapers 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., September-October 2005), but there was one hot paper identified from previous periods.

Using the current hot paper thresholds established by ESI as a benchmark, 11 hot papers, representing 1.0 % of the land/remediation papers, were identified in the fields of Environment/Ecology, Pharmacology & Toxicology, Engineering, and Biology & Biochemistry. The hot papers are listed in Table 14.

Table 14. Hot Papers Identified Using Current 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 land/remediation papers. Of the 14,477 total cites, 767 are author self-citesa 5.3% author self-citation rate. Garfield and Sher² found that authors working in research-based disciplines tend to cite themselves on the average of 20% of the time. MacRoberts and MacRoberts³ claim that approximately 10% to 30% of all the citations listed fall into the category of author self-citation. Therefore, the 5.3% self-cite rate for the land/remediation papers is well below the range for author self-citation.

¹ Thomson's Web of Science provides access to current and retrospective multidisciplinary information from approximately 8,500 of the most prestigious, high impact research journals in the world. Web of Science also provides cited reference searching.

² Garfield E, Sher IH. New factors in the evaluation of scientific literature through citation indexing. American Documentation 1963;18(July):195-201.

³ MacRoberts MH, MacRoberts BR. Problems of citation analysis: a critical review. Journal of the American Society of Information Science 1989;40(5):342-349.

Top of page