Impact Factor Of Journals: An Overview & The Concept of H-Index Dr. S. L. Sangam Professor and Chairman Department of Library & Information Science, Karnatak University Dharwad slsangam@yahoo.com

Impact Factor: An Overview

Introduction Impact factor was first described by Dr. Eugene Garfield in 1955. It is a measure of importance of scientific journals which is widely used to rank and evaluate journals. It is calculated by the Institute of Scientific Information (ISI) and published in Journal Citation Reports (JCR). Impact Factors have a huge, but controversial, influence on the way any published scientific research is perceived or evaluated. The usefulness of the Impact Factor measures in macro, meso and micro analysis is displayed. The Impact Factor of a certain journals is used as in proxy of the quality and expected impact of each of the papers published in it. Impact Factor is the only one of the three standardized measures created by the Institute out of Scientific Information (ISI) which can be used to measure the way the journal reviews citations to its articles over time.

Cont In many countries, Impact Factor is one of the criteria applied to evaluate not only the status of scientific journals, but also the publication output of scientists. Therefore, Impact Factor is basically a ratio between Citation and citable items published in a journal, and indicate the relative standing and influence of the journal within its disciplinary boundaries. As a result Impact Factor is frequently considered as an indicator of research quality and scientific excellence. Its use i.e. increasing not only amongst the bibliometric community, but also amongst the researchers and science policymakers.

Definitions According to Institute of Scientific Institution (ISI) "Impact factor is the number of current citations to articles published in a specific journal in a two years period divided by the total number of articles published in the same journal in the corresponding two years period." According to glossary of Thomson Scientific Terminology The term Impact Factor is defined as "The number of current citations to articles published in a specific journal in a two years period divided by the total number of articles published in the same journal in the corresponding two years period"

Cont According to Thomson Scientific ( 1994) "Impact Factor is the measure of the frequency with which the 'average article' in a journal has been cited in a particular year all period. The annual Journal Citation Reports (JCR) impact factor is a ratio between citations and recent citable items published. Thus the Impact Factor of a journal is calculated by dividing the number of current year citations to the source items published in that journal during the previous two years”.

Calculation The Impact Factor is generally calculated on the basis of a 3 year period. For example, the 2007 Impact factor for a journal would be calculated as follows: A = Number of times articles published in 2005-06 were cited in tracked journals during 2007 B = Number of articles published in 2005-06 2007 Impact Factor = A/B

Properties of Impact Factor ISI's wide international coverage which indexes almost all science and social science journals; Results are widely available to use and understand; There is an objective measure, and it has a widen acceptance than any of the alternatives; In practice the alternative measure of quality is "prestige". This rating by reputation, which is very slow to change, cannot be qualified or objectively used.

Applications of Impact Factor There have been many innovative applications of journal impact factors. The most common ones involve market research for publishers and others. But, primarily, Journal Citation Reports (JCR) provides librarians and researchers with a tool for the management of library journal collections. In market research, the impact factor provides quantitative evidence for editors and publishers for positioning their journals in relation to the competition--especially others in the same subject category, in a vertical rather than a horizontal or intradisciplinary comparison. JCR data may also serve advertisers interested in evaluating the potential of a specific journal

Cont The impact factor can be useful in all of these applications, provided that the data are used sensibly. It is important to note that subjective methods can be used in evaluating journals as, for example, by interviews or questionnaires. In general, there is good agreement on the relative value of journals in the appropriate categories. However, the JCR makes possible the realization that many journals do not fit easily into established categories. Often, the only differentiation possible between two or three small journals of average impact is price or subjective judgments such as peer review

Validity of Impact Factor The impact factor refers to the average number of citations per paper, but this is not a normal distribution. It is rather a Bradford distribution, as predicted by theory. Being an arithmetic mean, the impact factor is not a valid representation of this distribution, and is unfit for citation evaluation. In the short term especially in the case of low-impact-factor journals many of the citations to a certain article are made in papers written by the author(s) of the original article. This means that counting citations may be independent of the real “impact” of the work among investigators. Garfield, however, maintains that this phenomenon hardly influences a journal's impact factor. Similarly, journal self-citation is common in journals dealing in specialized topics, having high overlap in readership and authors, and is not necessarily a sign of low quality or manipulation.

Merits Of Impact Factor The use of Impact Factor as an index of journal quality depends on the fact that they are read / and that citation frequency actually measures a journal's importance to its user. It provides qualitative tools for ranking, evaluating category and comparing journals. There have been many innovative applications are Journal Impact Factor’s. It provides librarians and researchers with a tool for the selection and management of journal collections. It can be used to provide a gross approximation of the prestige of journals in which individuals have been published.

Cont Journal Impact Factor helps authors to decide where to submit their articles. Ranking is consistent within the field of study. Impact Factor is a simple metric, and provides a consistent way of comparing journals. The most important and recent use of impact is in the process of academic evaluation.

Demerits of Impact Factor Impact Factor gets misused often as it is sometimes used to just the appearance of the researchers. Since one cannot calculate impact factor with less than two years of date, new journals are left out of the list. The Impact Factor includes only journals indexed by Thomson Scientific. Review articles are generally cited more frequently than typical research articles because they often serve as surrogates for entire literature. A title change affects the Impact Factor for two years after the change is made. It does not distinguish between letters, reviews, or original research.

Cont It has inadequate international coverage as well as uneven coverage. Very few publications from languages other than English are included, and there are very few journals from the less developed countries. The number of citations to papers in a particular journal does not really directly measure the three quantitative aspects of a journal. Journals with low evaluation, regardless of the scientific merit of their contents, will never obtain high impact factors in an absolute science. An edition of a journal may encourage authors to rate the articles from that journal in the papers they submit. It is widely believed that importance or significance articles attract more Citation than other types of articles.

Conclusion The Impact Factor is a very useful tool for evaluation of journals, but it must be used very carefully. Journal Impact Factor is a good method for accessing the short- term scientific influence of journals. The value of Impact Factor is affected by the subject area, type and size of a journal, and the “window of measurement” used. The Impact Factor has also come to be used for many other purposes, some of which are an extension of the original purpose. Librarians use it for the selection of journals for their libraries. The interpretation of Impact Factor must be done with an understanding of its true meaning. Certain types of articles, such as reviews and technical reports, are more likely to be cited than such others, as case reports and pictorial essays. Thus, the Impact Factor has become a serious consideration in the selection of the journals to which some scientific researchers send their manuscripts.

The Concept of H-Index

Introduction Jorge E. Hirsch Professor of Physics at the University of California, San Diego, published an article describing the h-index, which he called “a useful index to characterize the scientific output of the researcher”. Hirsch (2005) proposes a scalar index, an original simple new indicator to characterize the cumulative impact of the research work of individual scientists. It is the highest number of publications of the scientists that received ‘h’ or more citations.

Cont It has immediately been recognized as an easily computable indicator for a scientist’s achievement because it incorporates both publication quantity and citation quality. It also provides good representation of the scientific lifetime achievement of the scientists as well as the simple calculations of the ‘h’ index using common literature database that leads to the danger of improper use of index. The h-index serves as an alternative to more traditional journal in the evaluation of the impact of the work of a particular researcher. Because only the most highly cited articles contribute.

Definitions The H-index is an index that attempts to measure both the scientific productivity and the apparent scientific impact of the scientists. The index is based on the set of scientists most cited papers and the number of citations that they have receive in others people’s publications. The index can also be applied to the productivity and impact of a group of scientists. ‘(1) According to Wapedia the H-index “is an index that attempts to measure both the scientific productivity and the apparent scientific impact of a scientist” (2) According to Hirsch, “A scientist has index ‘h’ if ‘h’ of his/her Np papers have at least h citations each and the other (Np-h) papers have no more than h citations each”

Types of Index H-Index The h-index that attempts to measure; both the scientific productivity and the apparent scientific impact of a scientist. The index is based on the set of the scientist’s most cited papers and the number of citations that they have received in other people’s publications. H-index eliminates the disadvantage of considering only single number criteria such as total number of papers or numbers of significant papers etc. H-index is proportional to academic age of the researches.

Cont G-Index: The g-index is an index for quantifying scientific productivity of scientists based on the distribution of citations received by a given researcher’s publications. G-index aims to improve on H-index by giving more weight to highly cited articles. It is as “Given a set of articles ranked in decreasing order of their citations”. The G-index is defined as largest number such that the top g articles received at least g2 citations

Cont W-Index: If all the papers of scientists are ranked in descending order of the number of citations they received the w-index is the highest number of papers one has that each received at least 10w or more citations. Thus the w-index can be defined as “A researcher has an index ‘w’ if ‘w’ of his/her papers have at least 10w citations each and other papers have fewer than 10 citations.

Cont A-Index: “A” index is simply defined as the average number of citations received by the publications included in the Hirsch core. The A-index more over uses the same data as the h-index so that the precision problem is exactly the same as for the original h-index and is not increased as in the case of g-index.

Applications of H-index Jorge Hirsch (2005) suggested that the h-index will be applicable at the micro level, that is, as a measure to quantify the scientific output of a single researcher. The h-index can be used not only for the lifetime achievements of a single researcher but can be applied to any publication set. VanRann (2006) calculated the h-index for University research group in chemistry and chemical engineering in the Netherlands. He is applying the index for quantification of scientific performance at the micro level but at the meso level.

Cont Braun, Glanzel and Schubert (2005) proposed for evaluating the scientific impact of journals as an alternative indicator to journal impact factors. The journal h index can be calculated as follows. Retrieving all sources items the number of a given year and sorting them by the number of times cited, it is easy to find the highest rank number which is still lower than the corresponding times cited value. Rousseau proposed calculation of a relative journal h-index, in that the h-index is divided by the number of paper published in the journal

Validity of the H-index Since the h-index is size-dependent, it could underestimate the accomplishment of “selective researchers”. A theoretical example of the h-index be in the case of the scientists with 10 documents cited 10 times each would have an h-index of 10, Scientists with 5 documents which are cited 200 times would have an h-index of 5. Scientists who publishes few documents, but their impact is much higher and Scientists who publishes more documents, but with a lower impact factor

Advantages of H-index It combines a measure of quantity (publication) and impact (citations). It allows us to characterize the scientific output of a researcher with objectivity and therefore may play an important role when making decisions about promotions, fund allocations and awarding prizes. It performs better than other single number criteria commonly used to evaluate the scientific output of a researcher (impact factor, total number of documents, total number of citations per paper rate and number of highly cited papers). The H-index can be easily obtained by anyone with access of science and in addition it is easy to understand.

Disadvantages of H-index There are inter-field differences in typical ‘h’ values due to differences among fields in productivity and citation practices, so the h-index should not be used to compare scientists from different disciplines. The h-index depends on the duration of each scientist’s career because the pool of publication and citation increases over time. Highly cited papers are important for the determination of the h-index, but once they are selected it belongs to top h papers, it is unimportant that numbers of citations they receive. This is the disadvantage of h-index. The use of the h-index could provoke changes in the publishing behavior of scientists such an artificial increase in the number of self citations distributed among the documents on the edge of the h-index.(VanRann 2006)

Conclusion The h-index is an interesting indicator the strength of which lies in the potential application for the assessment of papers were, traditional bibliometric indicators often proved problematic. The h-index is a cumulative indicator that does take neither the dynamics of the publication activity nor the ageing of the citation impact into account and that crashes the multidimensional into single dimension. The h-index is a supplementary indicator for the bibliometric toolset but the g-index can improve the h-index by giving more weight to highly cited articles.