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Bibliometrics is a type of research method used in library and information science. It utilizes quantitative analysis and statistics to describe patterns of publication within a given field or body of literature. Researchers may use bibliometric methods of evaluation to determine the influence of a single writer, for example, or to describe the relationship between two or more writers or works. One common way of conducting bibliometric research is to use the Social Science Citation Index, the Science Citation Index or the Arts and Humanities Citation Index to trace citations.
Laws of Bibliometrics | Citation Analysis | Resources and Links

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Laws of Bibliometrics

One of the main areas in bibliometric research concerns the application of bibliometric laws. The three most commonly used laws in bibliometrics are: Lotka's law of scientific productivity, Bradford's law of scatter, and Zipf's law of word occurrence.

Lotka's Law

Lotka's Law describes the frequency of publication by authors in a given field. It states that " . . . the number (of authors) making n contributions is about 1/n² of those making one; and the proportion of all contributors, that make a single contribution, is about 60 percent" (Lotka 1926, cited in Potter 1988). This means that out of all the authors in a given field, 60 percent will have just one publication, and 15 percent will have two publications (1/2² times .60). 7 percent of authors will have three publications (1/3² times .60), and so on. According to Lotka's Law of scientific productivity, only six percent of the authors in a field will produce more than 10 articles. Lotka's Law, when applied to large bodies of literature over a fairly long period of time, can be accurate in general, but not statistically exact. It is often used to estimate the frequency with which authors will appear in an online catalog (Potter 1988).

Bradford's Law

Bradford's Law serves as a general guideline to librarians in determining the number of core journals in any given field. It states that journals in a single field can be divided into three parts, each containing the same number of articles: 1) a core of journals on the subject, relatively few in number, that produces approximately one-third of all the articles, 2) a second zone, containing the same number of articles as the first, but a greater number of journals, and 3) a third zone, containing the same number of articles as the second, but a still greater number of journals. The mathematical relationship of the number of journals in the core to the first zone is a constant n and to the second zone the relationship is n². Bradford expressed this relationship as 1:n:n². Bradford formulated his law after studying a bibliography of geophysics, covering 326 journals in the field. He discovered that 9 journals contained 429 articles, 59 contained 499 articles, and 258 contained 404 articles. So it took 9 journals to contribute one-third of the articles, 5 times 9, or 45, to produce the next third, and 5 times 5 times 9, or 225, to produce the last third. As may be seen, Bradford's Law is not statistically accurate, strictly speaking. But it is still commonly used as a general rule of thumb (Potter 1988).

Zipf's Law

Zipf's Law is often used to predict the frequency of words within a text. The Law states that in a relatively lengthy text, if you "list the words occurring within that text in order of decreasing frequency, the rank of a word on that list multiplied by its frequency will equal a constant. The equation for this relationship is: r x f = k where r is the rank of the word, f is the frequency, and k is the constant (Potter 1988). Zipf illustrated his law with an analysis of James Joyce's Ulysses. "He showed that the tenth most frequent word occurred 2,653 times, the hundredth most frequent word occurred 265 times, the two hundredth word occurred 133 times, and so on. Zipf found, then that the rank of the word multiplied by the frequency of the word equals a constant that is approximately 26,500" (Potter 1988). Zipf's Law, again, is not statistically perfect, but it is very useful for indexers.

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Citation Analysis

Another major area of bibliometric research uses various methods of citation analysis in order to establish relationships between authors or their work. Here is a definition of citation analysis, and definitions of co-citation coupling and bibliographic coupling, which are specific kinds of citation analysis.

Citation Analysis

When one author cites another author, a relationship is established. Citation analysis uses citations in scholarly works to establish links. Many different links can be ascertained, such as links between authors, between scholarly works, between journals, between fields, or even between countries. Citations both from and to a certain document may be studied. One very common use of citation analysis is to determine the impact of a single author on a given field by counting the number of times the author has been cited by others. One possible drawback of this approach is that authors may be citing the single author in a negative context (saying that the author doesn't know what s/he's talking about, for instance) (Osareh 1996).

Co-citation Coupling

Co-citation coupling is a method used to establish a subject similarity between two documents. If papers A and B are both cited by paper C, they may be said to be related to one another, even though they don't directly cite each other. If papers A and B are both cited by many other papers, they have a stronger relationship. The more papers they are cited by, the stronger their relationship is.

Bibliographic Coupling

Bibliographic coupling operates on a similar principle, but in a way it is the mirror image of co-citation coupling. Bibliographic coupling links two papers that cite the same articles, so that if papers A and B both cite paper C, they may be said to be related, even though they don't directly cite each other. The more papers they both cite, the stronger their relationship is.

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Web Applications of Bibliometrics

Recently, a new growth area in bibliometrics has been in the emerging field of webmetrics, or cybermetrics as it is often called. Webmetrics can be defined as using of bibliometric techniques in order to study the relationship of different sites on the World Wide Web. Such techniques may also be used to map out (called "scientific mapping" in traditional bibliometric research) areas of the Web that appear to be most useful or influential, based on the number of times they are hyperlinked to other Web sites.

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Works Cited, and Other Useful Resources


Works Cited

Osareh, Farideh. "Bibliometrics, Citation Analysis and Co-Citation Analysis: A Review of Literature I." Libri 46 (September 1996), 149-158.
Highly recommended for a discussion of the history of bibliometrics, along with the development of the field and good definitions of commonly-used terms and techniques. Includes a lengthy bibliography.

Potter, William Gray. " 'Of Making Many Books There is No End': Bibliometrics and Libraries." The Journal of Academic Librarianship 14 (September 1988), 238a-238c (insert between 238 and 239).
Gives simple explanations of Lotka's Law, Bradford's Law, and Zipf's Law, aimed at a general library audience. Emphasizes the practical use of the laws in librarianship.

Other Useful Print Resources

Diodato, Virgil. Dictionary of Bibliometrics. New York: The Haworth Press, 1994.
In this, the only English-language dictionary of bibliometrics, Diodato explains about 225 terms, giving many cross-references and citing articles and books where the terms are used.

Hertzel, Dorothy Hoffstetter. "Bibliometrics, History of the Development of Ideas in." Encyclopedia of Library and Information Science, vol. 42, supplement 7, pages 144-211. New York: M. Dekker, 1987.
Truly exhaustive. A must for anyone seriously studying bibliometrics.

Osareh, Farideh. "Bibliometrics, Citation Analysis and Co-Citation Analysis: A Review of Literature II." Libri 46 (September 1996), 217-225.
A continuation of part I cited above, with discussion of the various types of co-citation analysis, scientific mapping, and the limitations of citation analysis as a research method.

Useful Links

Applications in Teaching Bibliometrics by Sara von Ungern-Sternberg. A discussion of the reasons behind and the methods of teaching bibliometrics to LIS students. Includes basic descriptions of the application of bibliometrics in a collection development context, and the main concepts in the field.

Bibliometrics, Scientometrics & Informetrics by Luc Quoniam. A list of related Web links.

Science and Technology Metrics by Dr. Ronald N. Kostoff at the Office of Naval Research. A full-text monograph discussing the use of metric research within the context of science and technology.


Examples of Bibliometric Research

Borgman, Christine L., ed. Scholarly Communication and Bibliometrics. Newbury Park, CA: Sage Publications, Inc., 1990.
A good general introduction to the field, this is a great place to look if you need examples of actual studies conducted using bibliometric methods--Look in Part III.

Bibliometric Mapping by the Centre for Science and Technology Studies (CWTS) at Leiden University in the Netherlands. Published results of bibliometric mapping projects.

BIRD: Bibliometric Retrieval of Documents, from the National Research Council Canada-Institute for Information Technology. BIRD is a bibliometric query by example search engine. Given a set of pages of interest to the user, it retrieves a set of similar documents by following citation paths that pass through those given documents.

BIRD Resources: Bibliometric Systems. A list of bibliometric systems, projects and links.

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