Annals of Library Science and Documentation Vol 41, 3; 1994; 81-94.

BIBLIOMETRIC ANALYSIS OF CORE JOURNALS ON IMMUNOLOGY:A STUDY BASED ON THE ANNUAL REVIEW OF IMMUNOLOGY

JAGDISH ARORADeputy LibrarianIndian Institute of TechnologyNew Delhi

SHARAN PAL KAURLibrarianMehta Instt. of Mathematical StudiesAllahabad

Bibliometric study on core journals on immunol-ogy derived from citations collected from the An-nual Review of Immunology for four consecutiveyears, i.e. 1983 to 1986 reveals very high con-centration of literature in a few scientific journals.The first four core journals contribute 47.96% oftotal citations while the first two top-ranked jour-nals account for close to 30% of total citations. Inaddition to determining country, subject, physicalformat, chronological and language distribution ofcore journals in immunology, the half-life and cita-tion peak of journals in immunology have also beenworked out. The scattering of literature in immu-nology is determined by applying Bradford's Law.The core journals in immunology and other disci-plines of biomedical sciences are also compared.

INTRODUCTION

Research in immunology as a basic science be-gan in the later quarter of nineteenth century asan insiqnificant branch of clinical microbiologywhen a group of microbiologists realized the im-portant role of immunology in the defense mecha-nism of body against infectious diseases. Later,researchers realized that allergies, too, had animmunological basis. The discipline did not growuntill World War \I when the joining of immunolo-gists with biochemists, cellular biologists and ge-neticists resulted in the invasion of immunologythat eventually led to the development of a unifiedconcept of immunological processes, and tothe establishment of immunology as a scientificdiscipline in its own right [1]. Immunology, thus, isan eclectic science that draws on many branchesof knowledge. The pursuit of research in modernimmunology requires a broad cross-disciplinaryknowledge-base with strong information back-upon the protein chemistry, modern cell-culture tech-niques, genetic engineering, microbiology, virol-ogy, nucleic acid chemistry and molecular andcellular biology. According to a conservative esti-

Vol. 41 No.3 September 1994

mate there are about 25,000 practicing immu-nologists in the-world today [2]. The Interna-tional Congress of Immunology, held on everyalternate year, has more number of participantsthan any other scientific conference with a totalattendance of over 12,000 during the 8th Interna-tional Congress held at Berlin, Germany in 1993[3]. The observation that 80% to 90% of all thescientists that have ever lived are alive now [4],seems to be correct for life scientists and espe-cially for irnrnunoloqists. Further, it is estimated thatjournals on immunology and its peripheral subjectspublish around 1,00,000 pages every year [5].

Problem of quantitative overload in biomedicalsciences is, however, well looked after by com-puterized databases like, MEDLARS, EM BASE,Cambridge Life Sciences Collection (all of themare available on CD-ROM). Since quality criteriaare not applied while inclusion of literature in thesedatabases, they are known to contain a substan-tive amount of irrelevant information of low qual-ity. The immediate need, it is felt, is not forbetter bibliographical control but for selection,evaluation and analysis of existing scientific lit-erature. It is known that the majority of significantcontributions in science is reported in a relativelysmall number of high-impact journals. Bibliometricmethods based on statistical analysis help toeliminate low quality literature and to select a smallportion of significant, reliable and relevant infor-mation. The techniques of bibliometrics offer anumber of effective indicators to quantify scien-tific research, to assess the scientific performanceand can be used in conjunction with the reviewprocesses.

The present study concerns with post publicationfiltration of scientific literature which includesbibliometric methods based on statistical analy-sis of citation patterns. Citations in a written docu-ment are empirical in nature and reflect the actual

81

JAGDISH ARORA and SHARAN PAL KAUR

practices of the authors. Hence, analysis of awide range of citation would reveal the readingusage pattern of literature of a community or abranch of it. Citation analysis gives quantitativesupport to the qualitative tests of time criterionthat "the longer a specific finding lasts, the bet-ter it is proved to be" [6]. It is specially applicableto the periodical literature because of continuityin their publication pattern. The present work de-termines qualitative journals on the basis of theirquantitative performance and ranks list of corejournals in immunology - their country, subjectcoverage, form and language distribution. It alsoevaluates scattering of concentration of literaturein immunology by applying Bradford's Law ofSattering/Garfields Law of Concentration to thecollected citations and finally, it compares thecore journals in immunology with core journals inother disciplines of biomedical sciences.

CREATION OF CITATION BASE

The citation for bibliometric analysis can be de-rived from any document or a set of documentswhich provide a list of referred documents. Mostof the bibliometric studies, however, derive theirraw data for analysis from a set of primary jour-nals on a chosen subject discipline. This methodof study of 'Citations collected from selected pri-mary journals suffers from a number of bias thatare characteristic to the items referred in primarymedia of communication. Some of the typicalproblems relate to self-citations, implicit citations,limit in the time period covered and the citationsgiven for reasons other than professional. Fur-ther, since the process of bibliometric analysis islabour-intensive the number of source journalsand citations collected are usually insufficient.Moreover, selection of periodicals for bibliometricanalysis based on the country and the languagescovered by them, may also affect the inferencesdrawn. On the contrary, the citations given in areview article do not suffer from the problems thatare characteristics to the citations obtained fromprimary journals. A review article is a transientminiature representing literature published in agiven subject. A review provides synthesis of theproliferating fragmented knowledge appearing ina plethora of publications. It carries a highlyanalytical, organized and complete synthesis ofinformation in a given area. The process of review-ing involves great amount of time and effort onthe part of experts in summarizing consensus ofscientific opinion on a given topic for simplifying

82

the task of documenting earlier research. Experts,to support the credibility of their views, cite high-est quality and the most relevant literature. More- .over, because of constraints of space, the num-ber of citations are severely limited and redun-dancy of citations is minimized in a review ar-ticle. Citations from reviewing literature as a sourceof citation for bibliometric analysis have thus beenpreferred to the citations from the primary jour-nals since the former as a source of citation isknown to have an edge over the later. Pao [7] ina study conducted in 1975 used review articlesas quality filters to identify recognized authori-ties in the field and also used the bibliographiesof these review articles to identify relevant andinfluential journals and text book literatures.Sengupta [8] elaborates factors favouring cre-ation of a citation base for bibliometric analysisfrom citations given in the annual reviews. The factthat citations collected from the reviewing litera-ture have a definite edge over the citations col-lected from primary literature was amply estab-lished in a related study reported elsewhere [7A].The analysis conducted on the citation baseconsisting of citations collected from reviewingliterature revealed that 22 out of 116 (18.97%)most-cited authors and 33 out of 128 (28.45%)most-cited articles identified in the study alreadyhad the distinction of being most-cited amongstmillions of citations processed in the ScienceCitation Index (SCI) database. The significanceof this observation increases many-fold whenviewed in the light of following facts:

(i) In 1988, the SCI database consisted of morethan 175 million cited references derivedfrom more than 15 million source articles;

(ii) In the SCI database approximately 5,00,000(2.00%) source articles received 50 or morethan 50 citations. 1000 articles having morethan 664 citations and identified as most-citedfrom this database during 1961-1982 ac-counted for more than 1,500,000 citations;

(iii) Most-cited articles from the SCI databaseare not restricted to one discipline. They, in-stead represent the entire scientific and tech-noloqical enterprise. A few studies referredabove, however, dealt with life sciences sepa-rately;

(iv) 1000 most-cited articles from SCI database forthe period 1961-1982 was just 0.004% of over

Ann Lib Sci Doc

BIBLIOMETRIC ANAL YSIS OF CORE JOURNALS ON IMMUNOLOGY

23 million different publications cited in theSCI during the period; and

(v) 50% of the most-cited articles from the SCIdatabase are papers on methodology ormodified methodology. Similarly, citations toreview articles in the SCI database is quitesignificant.

The Annual Review of Immunology, started in1983 by Annual Reviews Inc., is an importantreviewing journals in the field of immunology andhas been selected to obtain citations data foranalysis in this study. At present, Annual Re-views, Inc. publishes 27 different volumes cov-ering such diverse topics as genetics, nutri-tion, material sciences, computer science andpsychology.

Methodology

The citation base was obtained by collecting cita-tions from each chapter of the Annual Review ofImmunology (vols. 1-4, 1983-1986). The refer-ences given at the end of each chapter werexeroxed and each citation was then transferred inoriginal (cut and paste) to 3" X 5" slips, eliminat-ing the chances of error which might have oc-curred otherwise. Identification of journal titles wasdone using 28th edition of Ulrich's InternationalPeriodical Directory (including Irregular Serials)and the World List of Scientific Periodicals.MEDLARS, EM BASE and Compact Cambridge:Life Science Collection databases available onCD-ROM at the National Institute of Immunologyand the Indian MEDLARS Centre were used tosearch for the incomplete/inadequate citations.

The citations collected from B7 articles publishedin the Annual Review of Immunology between1983 and 1986 totaled to 10830 including 10024(92.56%) citations to articles published in primaryliterature and B06 citations to other forms ofpublications. The citations, thus obtained, werearranged journal-wise in decreasing frequency ofcitation counts of each journal.

BIBLIOMETRIC ANALYSIS ON RANKED LISTOF CORE PERIODICALS

Core Journals on Immunology

Table 1 shows 66 core journals in the field of

Vol. 41 No.3 September 1994

immunology arranged in decreasing frequency ofcitations. In cases of ties, i.e., if the citationsreceived by two or more journals are same, theimpact factor has been taken into consideration.As can be seen, the ranked lists of journals inimmunology has deliberately been restricted to66 journals. Remaining 359 journals have notbeen included in the ranked list as each of themhad very insignificant number of citations totheir credit. The ranked list indicates that the Jour-nal of Immunology and the Journai of Experi-mental Medicine are two highly cited journals thatoccupy two top slots in the ranked lists ofperiodicals. The two journals between them-selves account for 29.68% of total citations(Journal of Immunology : 15.78% and Journalof Experimental Medicine: 13.90%). Garfield [9]in a study which compared citation patterns of theJournal of Experimental Medicine and the Journalof Immunology observed that no other journalseemed to playas important role today in thetransfer of information in immunology as doesthe Journal of Experimental Medicine. Inspite ofgenerality of its title, the journal essentiallypublishes articles in immunology. The Journal ofExperimental Medicine, he opined, is one of themost-cited journals in the world and it ranks high-est in terms of its impact. In an another study,Garfield [10] analyzed the citation performanceof 6,500 articles published in the Journal of Ex-perimental Medicine from 1955 to 1985. Thestudy reflected that 2,900 or 44% of total articlespublished in the Journal of Experimental Medi-cine during the period were cited over 50 times.Although, in comparison to the other journals,the Journal of Experimental Medicine has pub-lished far fewer articles, nevertheless its citationperformance makes it a journal extraordinaire.Further, as per the Journal Citation Report,based on analysis of citations from 4,39B jour-nals and other publications available in ISI data-base, the Journal of Experimental Medicine wascited over 37,079 times while the Journal ofImmunology was cited 64,358 times till 1988.Comparing the citation figure of the two journalsin terms of their impact as analyzed in theJournal Citation Report [11], the Journal of Experi-mental Medicine ranks 22nd with impact factor

. of 11.83 and the Journal of Immunology ranks53rd with impact factor of 6.9 amongst 4,398journals.

83

JAGDISH ARORA and SHARAN PAL KAUR

Table 1

Ranked list of periodicals on Immunology

Rank Name of journal Year of Country Citations %of Cumm. %ofno. inception received Col. 5 citation Col. 7(1 ) (2) (3) (4) (5) (6) (7) (8)

1. J.lmmunol. 1916 USA 1582 15.78 1582 15.7822. J. Exp. Med. 1896 USA 1393 13.90 2975 29.6793. Nature 1869 UK 938 9.36 3913 39.0364. Proc. Nat. Acad. Sci. 1915 USA 894 8.92 4807 47.9555. Cell 1974 USA 382 3.81 5189 51.7666. Europ. J. Immunol. 1970 FRG 359 3.58 5548 55.3477. Science 1883 USA 290 2.89 5838 58.2408. Immunol. Rev· 1969 Denmark 232 2.31 6070 60.5559. J. BioI. Chem. 1905 USA 224 2.23 6294 62.78910. J. Clin. Invest. 1924 USA 133 1.33 6427 64.11611. Immunology 1958 UK 133 1.33 6560 65.44312. Mol. Immunol.!! 1964 USA 133 1.33 6693 66.77013. Cell. Immunol. 1970 USA 123 1.23 6816 67.99714. N. England J. Med. 1812 USA 107 1.07 6923 69.06415. Immunogenetics 1974 USA 98 0.98 7021 70.04216. Biochemistry 1964 USA 95 0.95 7116 70.99017. Transplantation 1963 USA 92 0.95 7208 71.90718. Lancet 1823 UK 86 0.86 7294 72.76519. Ann. Rev. Immunol. 1983 USA 81 0.81 7375 73.57320. Adv. Immunol. 1961 USA 81 0.81 7456 74.38121. Fed. Proc. 1942 USA 79 0.79 7535 75.17022. Scand. J. Immunol. 1972 UK 71 0.71 7606 75.87823. Clin. Exp. Immunol. 1966 UK 70 0.70 7676 76.57624. Infect. Immun. 1970 USA 67 0.67 7743 77.24525. EMBO J. 1982 UK 66 0.66 7809 77.90326. Diabetes 1952 USA 62 0.62 7871 78.52227. Nucleic Acids Res. 1974 UK 53 0.53 7924 79.05028. Biochem. J. 1906 UK 47 0.47 7971 79.51929. Cold Sprng. Harb. Symp.

Quant.Biol. 1933 USA 46 0.46 8017 79.97830. Arthr. Rheum. 1958 USA 45 0.45 8062 80.42731. Ann. N Y Acad. Sci. 1823 USA 45 0.45 8107 80.87632. J. Cell Biol.$ 1955 USA 43 0.43 8150 81.30533. Biochem. Biophys. Res.

Commun. 1959 USA 42 0.42 8192 81.72434. Transplant Proc. 1969 USA 41 0.41 8233 82.13335. Biochem. Biophys. Acta 1947 Holland 39 0.39 8272 82.52236. J. Mol. BioI. 1959 UK 38 0.38 8310 82.90137. Cancer Res. 1941 USA 37 0.37 8347 83.27038. Blood 1946 USA 36 0.36 8383 83.62939. Clin. Immunol.

Immunopathol. 1972 USA 36 0.36 8419 83.98840. Proc. Soc. Exp. BioI. Med. 1903 USA 33 0.33 8452 84.318

Contd.

84 Ann Lib Sci Doc

BIBLIOMETRIC ANAL YSIS OF COl'fE JOURNALS ON IMMUNOLOGY

Table 1 (Contd.)

Rank Name of journal Year of Country Citations %of Cumm. %01no. inception received Col. 5 citation Col. 7(1) (2) (3) (4) (5) (6) (7) (8)

41. Ann. Rev. BioC:hem. 1931 USA 31 0.31 8483 84.62742. Diabetelogia 1965 FRG 31 0.31 8514 84.93643. J. Nat. Cancer Inst. 1940 USA 31 0.31 8545 85.24544. Immunol. Today 1980 UK 29 0.29 8574 85.53545. Int. J. Cancer 1966 USA 29 0.29 8603 85.82446. Am. J. Pathol.% 1924 USA 27 0.27 8630 86.09347. Ann. Intern. Med. 1922 USA 26 0.26 8656 86.35348. Am. Rev. Respiratory Dis.! 1917 USA 26 0.26 8682 86.61249. Int. Arch. Allergy Appl.

Immunol. 1950 Switzerland 25 0.25 8707 86.86250. Clin. Res. 1953 USA 23 0.23 8730 87.09151. Mol. Cell. BioI. 1981 USA 22 0.22 8752 87.31052. Prog. Allergy 1966 Switzerl 22 0.22 8774 87.53053. J Allergy Clin. Immunol. 1929 USA 22 0.22 8796 87.74954. Proc. Royal Soc. (London)

B. BioI. Sci. 1905 UK 22 0.22 8818 87.96955. Ann. Inst.

Pasteur/lmmunol. %% 1887 France 22 0.22 8840 88.18856. J. Investigative Dermatol. 1938 USA 21 0.21 8861 88.39857. Springer Sem.

Immunopathol. 1978 FRG 21 0.21 8882 88.60758. Nature-New Biol.** 1869 UK 21 0.21 8903 88.81759. Neurology 1951 USA 20 0.20 8923 89.01660. Australian J. Exp.

BioI. Med. Sci. 1924 Australia 20 0.20 8943 89.21661. J. Infectious Dis. ·1904 USA 19 0.19 8962 89.40562. J. Immunol. Methods 1971 USA 19 0.19 8981 89.59563. FEBS Letters 1968 Holland 18 0.18 8999 89.77564. Immunobiology 1909 FRG 18 0.18 9017 89.95465. Prostaglandlins 1972 USA 18 0.18 9035 90--13466. Arch. Dermatol. 1920 USA Ht o.rs 9053 90.313

><:.

Formerly Transplantation ReviewFormerly Am. Rev. Tuber. Pulmon. Dis.

$ Formerly J.Biochem. Biophys. Cytol.!! Formerly Immunochemistry

Vol. 41 No.3 September 1994 85

JAGDISH ARORA and SHARAN PAL KAUR

Subject-wise Distribution of Core Journals

Subject-wise distribution of journals in the field ofimmunology for the core journals is given inTable 2.

Table 2

Subject-wise distribution of core journals onImmunology

SI. Subject categoryno. of journals

No. of titles % ofcited in Ann. TotalRev. Immunol.

(ARI)

1. Immunology (General) 21 31.822. Medical Sciences 22 33.333. Basic Biology, Biochem. 12 18.184. Mol. and Cell. Biology 7 10.615. General Sciences 4 06.06

Total 66 100.00

A sizable representation of journals of medicalsciences in the core journals of immunology ex-plain the proximity of two subjects. Immunologycontinues to be an important discipline taughtin medical sciences and has contributed sub-stantially in combating a number of fatal diseasesof epidemic nature through vaccines which havetangible application in medical sciences. SCl'sJournal Citation Report (1988) reveals substan-tial amount of citations by clinical journals to theJournal of Experimental Medicine and the Journalof Immunology as well as other journals on im-munology which illustrates the role and impact ofbasic research in clinical applications. Repre-sentation of journals from various other disci-pline of life sciences in the core list of journalsin immunology ascertains the fact that immunol-ogy is an eclectic science drawing on biochemis-try, cellular and molecular biology, medicine, ge-netics, etc. Further, several top-ranked journals inthe ranked list are exclusively devoted to generalor applied immunology which goes on to provethe well established status of immunology in sci-entific research. Publication of articles in generalscience journals may be interpreted as indica-tion of present role of immunology in the ad-vancement of fundamental sciences.

86

Language Distribution of Core Journals in Im-munology

.Language distribution of literature provides majorvehicles for dissemination in the subject put to theanalysis. Earlier studies of periodical publicationin sciences have shown that the English, Rus-sian, German, French and Japanese dominatethe publication scenario and usually in that ordertoo. The findings of the present study, however,shows that 61 out of 66 (92.42%) of core journalsin immunology are published in English languagewhile the remaining 5 (7.58%) are multilingual, i.e.they publish in Enqlish, French, German andSpanish. This shows that the English is the lin-gua-franca of communication for immunologists.

Country-wise Distribution of Core Journals inImmunology

A geographic analysis of citations furnishes infor-mation on the range of countries active in a sub-ject field and their relative contribution.Bibliometrically, the value of place of publicationrests very much with its ability to point to the'nationality' of a document. Place of publication isthe best guide available to nationality of a docu-ment. From this information an impression of'scatter' can be obtained. Table 3 gives country-wise distribution of core journals in immunologyfor the three sets of core journals. While USA

Table 3

Country-wise distribution of core journals onimmunology

SI. Country Ann. Rev. Percentageno. of origin Immunol.

1. USA 43 65.1512. UK 12 18.1813. Denmark 1 1.5154. United Germany 4 6.0605. The Netherlands 2 3.0306. Switzerland 2 3.0307. France 2 3.030

Total 66 100%

takes the top position with its contribution hover-ing at 65.15% (43 journals), th~ UK is second onthe lists of countries contributing to with 12

Ann Lib Sci Doc

BIBLIOMETRIC ANAL YSIS OF CORE JOURNALS ON IMMUNOLOGY

journals (18.18%). Germany stands third with 4core journals (6.06%). The Netherlands, Franceand Switzerland contribute two core journals eachto the ranked list while Denmark contributes onejournal to the core list of journals.

Bibliographical Forms of Cited Documents

Each document type or form has a specific role toplay in dissemination of information and it is thisrole that dictates the nature, level and currency ofinformation carried, as well as physical format andthe frequency with which it is published. A pre-ponderance of journals suggests that the subjecthas a high turnover of ideas. A number of continu-

ing developments requires current news and in-formation and that, results of research or studycan be best accommodated by the article typeof format of the journals. The articles publishedin journals accounts for 10024 citations (92.558%).Citations to books and monographs constitute4.432% (480 citations), while published proceed-ings are cited 98 times (0.905%). Citations to ir-regular serials are 1.163% (126 citations). Pa-pers in preparation, unpublished observation, etc.has its representation with 77 citations (0.711 %).Dissertation/theses are cited 11 times (0.102%)while reports received 14 citations (0.129%).Table 4 gives the distribution of bibliographicalforms of cited documents.

Table 4

Distribution of citations based on bibliographic forms

SI. no. Form of document PercentageAnn. Rev.Immunol.

1.2.3.4.5.6.7.

JournalsBooksPublished proceedings of the symposia/conferencesIrregular SerialsPapers in preparation/unpublished observationDissertationsReports and Monographs

92.5584.4320.9051.1630.7110.1020.129

10024480

98126771114

Total 100%10830

Year-wise Distribution of Citations and Age-ing of Journal Collection

A number of studies have revealed that gener-ally the recent volumes of a current journal seemto be used more often than the older ones. Sev-eral studies have been carried out to measure theuse of back volumes of periodicals in order tooptimize holdings of back volumes of periodicalsor for discarding the old files of journals which

Vol. 41 No.3 September 1994

were used sparingly in the past. Burton and Kebler[13] defined the half-life of periodical literature as"the time during which half of all currently activeliterature was published". On the basis of thisdefinition, the half-life of journals in immunologywas determined to be less than six years sincemore than half of the total citations (54.61%)belonged to 1981-1987 period. The year-wisedistribution of citations is given in Table 5 indescending chronological order.

87

JAGDISH ARORA and SHARAN PAL KAUR

Table 5

Year-wise distribution of citations in immunology

Period Year Citations % Cumulative 0/0(in years) received of Col. 3 citations of Col. 5

(1) (2) (3) (4) (5) (6)

1 1987 3 0.030 3 0.0302 1986 60 0.599 63 0.6283 1985 623 6.215 686 6.8444 1984 1043 10.405 1729 17.2495 1983 1305 13.019 3034 30.2676 1982 1326 13.228 4360 43.4967 1981 1114 11.113 5474 54.6098 1980 899 8.968 6373 63.5779 1979 637 6.355 7010 69.932

10 1978 509 5.078 7519 75.01011 1977 433 4.320 7952 79.33012 1976 375 3.741 8327 83.07113 1975 270 2.694 8597 85.76414 1974 210 2.095 8807 87.85915 1973 167 1.666 8974 89.52516 1972 159 1.586 9133 91.11117 1971 146 1.457 9279 92.56818 1970 106 1.057 9385 93.625

19-2a 1969-60 413 4.120 9798 97.74529-38 1959-50 152 1.516 9950 99.26239-48 1949-40 28 0.279 9978 99.54149-58 1939-30 25 0.249 10003 99.79159-68 1929-20 10 0.100 10013 99.89069-78 1919-10 6 0.060 10019 99.95079-88 1900-09 3 0.030 10022 99.98089-98 1898-75 2 0.020 10024 100.000

The data makes it obvious that the older researchpaper received fewer citations than the recentones. The year-wise distribution of citations var-ies from a maximum of 1326 (13.23% in 1982),followed by 1305 (13.02%) and 1114 (11.12%) in1983 and 1981 respectively to minimum of onecitation to a number of research papers publishedduring 19th century or during first three decadesof present century. The oldest cited article was

88

published in 1874 and the citations to resarcharticles published from 1874 to 1949 were between1 and 28. A gradual and steady increase in cita-tions to the articles published from 1950 onwardsis quite evident from the Table. Figures 1 and2 depict year-wise distribution of citations inimmunology on the basis of citations collected fromthe Annual Review of Immunology.

Ann Lib Sci Doc

BIBLIOMETRIC "ALYSIS OF CORE JOURNALS Ot. IMMUNOLOGYrtJZo 12 ~------------------------------------~•••8~ 10•••Uill I 8o ]. 8016Z ~

nI .c> f-4 4•••8~ 2

Jl O~~--~~--~~--~--~~--~~~J 0{l

10 20 30 40 50 60 70 80 90 100 110PERIOD IN NO. OF YEARS

Fig. 1 : Year-wise Distribution of Citations in Immunology

1500 r-------------------------------------------~~~ .

>Z 1000<ZM

f/J

Zo 500M

~

~•••U

1987 1985 1983 1981 1979 1977 1975 1973 19711986 1984 1982 1980 1978 1976 1974 1972 1970

YEARS OF CITEDARTlCLBS

Fig. 2 : Year-wise Distribution of Citations (Citation Decay Curve)

Vol. 41 No.3 September 1994 89

JAGDISH ARORA and SHARAN PAL KAUR

TESTIFYING BRADFORD'S LAW OF SCATTER-ING OF LITERATURE

Bradford's [14] empirical law of concentration forarticles in the scientific periodicals proved to be alandmark event in the field of bibliometrics.Bradford's law states that the articles on a givensubject concentrate heavily in a relatively smallcore of highly productive journals. "If scientificjournals are arranged in order of decreasing pro-ductivity of articles on a given subject, they maybe divided into a nucleus of periodicals moreparticularly devoted to the subject, and severalgroups of zones containing the same number ofarticles as the nucleus, when the number of peri-odicals in the nucleus and suceeding zones willbe as 1:n:n2: ... " [15].

This law provides a very convenient base forestimating the size of a subject literature and ameans of estimating how many journals mustbe checked to obtain a specified degree of com-pleteness. A general form of this law says that thecumulative number of papers on a given subjects(R (n)) will be related to the n journals in whichthey appear:

R (n) R (1) + K.log (n)

Table 6 represents journals arranged in decreas-ing order of frequency of citations received fromthe Annual Review of Immunology. 425 journalsreferred to in the Review, volumes 1-4 yielded10,024 citations. Bradford's Law of Scatteringis testified by plotting a graph by taking cumula-

Table 6

Distribution of cited journals in decreasing order of citationsAnnual Review of Immunology (1983-1986)

No. of Cumulative Log of 2 No. of Total no. Cumulative %of2 %of6journals. no. of citations citations no. of

journals citations1 2 3 4 5 6 7 8

1 1 0.000 1582 1582 1582 0.235 15.7821 2 0.301 1393 1393 2975 0.471 29.6791 3 0.477 938 938 3913 0.706 39.0361 4 0.602 894 894 4807 0.941 47.9551 5 0.699 382 382 5189 1.176 51.7661 6 0.778 359 359 5548 1.412 55.3471 7 0.845 290 290 5838 1.647 58.2401 8 0.903 232 232 6070 1.882 60.5551 9 0.954 224 224 6294 2.118 62.7893 12 1.079 133 399 6693 2.824 66.7701 13 1.114 123 123 6816 3.059 67.9971 14 1.146 107 107 6923 3.294 69.0641 15 1.176 98 98 7021 3.529 70.0421 16 1.204 95 95 7116 3.765 70.9901 17 1.230 92 92 7208 4.000 71.9071 18 1.255 86 86 7294 4.235 72.7652 20 1.301 81 162 7456 4.706 74.3811 21 1.322 79 79 7535 4.941 75.1701 22 1.342 71 71 7606 5.176 75.8Z81 23 1.362 70 70 7676 5.412 76.5761 24 1.380 67 67 7743 5.647 77.2451 25 1.398 66 66 7809 5.882 77.903

Contd.

90 Ann Lib Sci Doc

BIBLIOMETRIC ANAL YSIS OF CORE JOURNALS ON IMMUNOLOGY

Table 6 (Contd.)

No. of Cumulative Log of 2 No. of Total no. Cumulative %of2 %of6journals no. of citations citations no. of

journals citations1 2 3 4 5 6 7 8

1 26 1.415 62 62 7871 6.118 78.5221 27 1.431 53 53 7924 6.353 79.0501 28 1.447 47 47 7971 6.588 79.5191 29 1.462 46 46 8017 6.824 79.9782 31 1.491 45 90 8107 7.294 80.8761 32 1.505 43 43 8150 7.529 81.3051 33 1.519 42 42 8192 7.765 81.7241 34 1.531 41 41 8233 8.000 82.1331 35 1.544 39 39 8272 8.235 82.5221 36 1.556 38 38 8310 8.471 82.9011 37 1.568 37 37 8347 8.706 83.2702 39 1.591 36 72 8419 9.176 83.9881 40 1.602 33 33 8452 9.412 84.3183 43 1.633 31 93 8545 10.118 85.2452 45 1.653 29 58 8603 10.588 85.8241 46 1.663 27 27 8630 10.824 87.0932 48 1.681 26 52 8682 11.294 86.6121 49 1.690 25 25 8707 11.529 86.8621 50 1.699 23 23 8730 11.765 87.0915 55 1.740 22 110 8840 12.941 88.188

'3 58 1.763 21 63 8903 13.647 88.8172 60 1.778 20 40 8943 14.118 89.2162 62 1.792 19 38 8981 14.588 89.5954 66 1.820 18 72 9053 15.529 90.3131 67 1.826 16 16 9069 15.765 90.4731 68 1.833 15 15 9084 16.000 90.6233 71 1.851 14 42 9126 16.706 91.0423 74 1.869 12 36 9162 17.412 91.4016 80 1.903 10 60 9222 18.824 91.9998 88 1.944 9 72 9294 20.706 92.7177 95 1.978 8 56 9350 22.353 93.2768 103 2.013 7 56 9406 24.235 93.8356 109 2.037 6 36 9442 25.647 94.194

25 134 2.127 5 125 9567 31.529 95.44116 150 2.176 4 64 9631 35.294 96.07935 185 ~.267 3 105 9736 43;529 97.12748 233 2.367 2 96 9832 54.824 98.085

192 425 2.628 1 192 10024 100.000 100.000

tive number of citations R(n) on the ordinate tion of Bradford's Law of Scattering. The up-against the logarithm of cumulative number of ward curving bottom of the bibliograph repre-journals log (n) on the abscissa. It is observed sents the small nuclear zone of the most relevantthat the resulting bibliograph, initially starts with journals. The upper end of the curve representsthe rising as in exponential nature and then, fol- the peripheral zone where relevant references arelows into a linear curve indicating the observa- widely scattered among a large number of jour-

Vol. 41 No.3 September 1994 91

JiGDISH ARORA and SHARAN PAL KAUR

nals. It should be noted that the empiricial data infig. 3 be-jin to droop away from a straight line.This droop is characteristics of Bradford's plots andis called the Groos Droop. Groos [16] first noticedthat the bibliograph eventually form a curve whichdroops below the linear prediction of the BradfordLaw. It can be interpreted either as a measure of

incompleteness of the search if a complete bibli-ography on a subject is being testified, or as re-lated to the infiniteness of the population of jour-nals and papers. Since the empirical curve droopsbelow the straight line, the empirical data indicatethat fewer journals actually have one or more ar-ticles in immunology.

II

10

9111Z 150

~•.. 70,."",.0" 6.io·z:J

~l e

4:5~ ~::IU

:l

0.4 0.15 1.2 1.6 :lLOG. OF CUWULAllV£ NO. OF JKNL5.

Fig. 3 : Bradford's BibliographCitations from Annual Review of Immunology (1983-86)

o

Comparative Study of Core Journals in Bio-medical Sciences

Comparison between the core journals in immu-nology and other disciplines of biomedical sci-

ences has been made to find out correlationamongst them.

The comparison of citations collected from first 35core journals in immunology with that of bio-

Table 7

Citations received by first 35 core journals in biomedical sciences

Period Discipline Cumulative Cumulative Number of % of citationcovered number of number of citations in in 35 core

journals citations 35 journals journals

1968-70 Biochemistry 533 16,276 13,221 81.251968-70 Microbiology 624 8,951 6,323 70.621968-70 Physiology 633 9,814 6,297 64.161968-70 Pharmacology 781 9,596 5,297 55.171965-69 Medicine 975 14,201 7,510 52.871983-86 Immunology 425 10,024 8,272 82.52

92 Ann Lib Sci Doc

chemistry, microbiology, physiology, pharmacol-ogy and medicine identified by Sengupta usingannual review [17] reveals that 35 core journalsin the respective discipline of biomedical sciencesaccount for 82.52, 81.25, 70.62, 64.16, 55.17and 52.87% of total citations respectively. Thisreveals that the proliferation and concentration

of literature in 35 core journals of these two dis-ciplines i.e., immunology and biochemistry is muchhigher in comparison to the other disciplines ofbiomedical sciences. Further, all the six disci-plines of biomedical sciences share six journalswith core journals of immunology (Table 8).

Table 8

Six core joumals common to biomedical sciences, showing their rank and percentage of citations

51. Common core Immunology Medicine Biochemistry Microbiology Physiology PharmacologyNo. journals 1 2 1 2 1 2 1 2 1 2 1 2

1. Nature 3 9.36 7 2.18 6 4.52 4 5.05 5 3.01 2 4.262. Proc. Nat. Acad. Sc. 4 8.92 33 0.66 2 8.44 2 6.92 28 0.66 8 0.853. Science 7 2.89 15 1.48 9 3.28 10 2.42 8 2.48 5 2.554. J. BioI. Chem. 9 2.24 28 0.91 1 13.48 6 3.94 21 0.88 10 1.755. Fed. Proc. 21 0.79 11 1.52 12 1.98 30 0.57 11 2.09 9 2.216. Ann. NY Acad. Sc. 30 0.45 17 1.34 28 0.44 25 0.74 23 0.80 8 2.26

1 denotescore rankof a journal2 denotes% of citationreceivedin variousdiscipline

All the six journals excepting J. BioI. Chem. be-long to general sciences category. Further, fourof the six journals are amongst first ten journalsof the ranked lists in at least five disciplines ofmedical sciences including immunology. Besidesthese six journals, there are ten more journalsfeaturing amongst first thirty five core journalsin more than three disciplines of biomedical sci-ences. That means there are sixteen journals outof thirty five core journals that are common tovarious well established disciplines of biomedicalsciences. The significant overlap in the cover-age of these journals conforms to the Garfield'sLaw of Concentration [18] which states that thetail of the literature of one discipline consists of alarge part of the cores of the literature of theother disciplines.

CONCLUSION

Majority of significant contribution to the world ofscience are known to be reported in a relativelysmall number of high impact journals in a givenspeciality. The citations, as indicators of scientific

Vol. 41 No.3 September 1994

'quality' or 'importance' can be used for measur-ing the impact of a scientist or an article or anorganization or a publishing journal on the scien-tific and technical development. For decades, li-brarians have used citation counts to determinethe adequacy of a collection of periodicals, theoptimum size. of backfiles, binding and retentionschedules and for cost-benefit analysis in themanagement of subscription budget.

The citations collected from the review litera-ture have a definite edge over the citations col-lected from other sources. Ranking of periodicalsbased on the quantitative consideration as judgedby the frequency of citation counts is a simple tech-nique that can be used as a guidance to theacquisition policy of periodicals. Ranked list ofcore journals consisting of 10024 references toarticles published in periodicals accounts for9053 citations (90.313%). The ranked list of coreperiodicals thus developed in order of citationsreceived by them provide most objective and un-biased data regarding the performance of periodi-cals and thus, may be put to practical use for as-

93

JAGDISH ARORA and SHARAN PAL KAUR

sessing the effectiveness of a periodical collection.Acquisition policy especially for periodicals canbe based on qualitative considerations as judgedby ranking of periodicals on the basis of frequencyof citation counts.

Bibliometric methods based on statistical analy-sis can, thus, be used for eliminating low-qualityliterature and to select a small portion of signifi-cant, reliable and relevant high-quality publica-tions. A quality information system can, thus, bedesigned to allow a user to access its resourcesat a given threshold of quality using core periodi-cals in a given subject selected on the basis oftheir bibliometric performance while the systemwould still permit access to entire literature, if sodesired. It is believed that redundancy of the bio-medical literature is so great that probably littlewould be lost by using only core periodicals in agiven subject for a database.

REFERENCES1. KLEIN (J). Immunology: the science of

self-nonself discrimination. 1985. John Wiley;New York. p. 664-665.

2. Ibid. p. 663.

3. PROGRESS IN IMMUNOLOGY IX. 1993.Academic Presss; New York. 6 vols.

4. PRICE (0 J D). Science since Babylon.Enlarged 2nd edition. 1961. Yale UniversityPress; New Haven.

5. KLEIN (J). Op. Cit. p.664.

6. GARFIELD (E). Citation indexing; its theoryand application in science, technology and hu-manities. 1979. John Wiley; New York. p.241.

7. PAO (M L). A quality filtering system for medi-cal literature. Jour. Med. Educ. 50; 1975; 353-359.

7A. PAWAN (Usha) and ARORA (Jagdish). Most-cited research articles in immunology: abibliometric study of citations from the review-ing literature. A paper presented at the Fourth

94

International Conference on the Bibliometrics,Informatrics and Scientometrics 11 - 15thSept., 1993, Berlin, Germany.

8. SENGUPTA (I N). A new bibliometric tech-nique for quantitative evaluation of core jour-nals ofbaac bi:m ed±:al s:::::Enres. In: GUHA(B) Ed: The library and information sciencehorizon. 1986. Allied; New Delhi. p. 329-368.

9. GARFIELD (E). Journal citations studies. III.Journal of Experimental Medicine comparedwith Journal of Immunology, or how much ofa clinician is the immunologists. In: The essayof an information scientist. 1973. Vol. 1. ISI;Philadelphia. p. 326-329.

10. GARFIELD (E). Ninety-one citation classicsfrom the Journal of Experimental Medicine.Current Contents. 28; 1987; 3-13.

11. JOURNAL CITATION REPORT. 1988. ISI;Philadelphia.

12. LINE (M B) and SANDISON (A). A practicalinterpretation of citation and library use stud-ies. Coli. Res. Lib. 36, 5; 1975; 393-396.

13. BURTON (R E) and KEBLER (R W). Thehalf-life of some scientific and technical lit-erature. Amer. Docum. 11, 1; 1960; 18-20.

14. BRADFORD (S C) Sources of information onspecific subjects. Engineering. 137; 1944; 85-86.

15. BRADFORD (S C) Documentation. 1948.Crosby Lockwood & Son Ltd.; London.

16. GROOS (0 V). Bradford's law and theKeenan-Atherton data. Amer. Docum. 18;1967; 46.

17. SENGUPTA (I N) Op. Cit.

18. GARFIELD (E). The mystry of the transposedjournal lists: wherein Bradford's law of scat-tering is generalized according to Garfield'slaw of concentration. In: The essays of aninformation scientist. 1977; Vol. 1. ISI; Phila-delphia. p. 222-223.

Ann Lib Sci Doc