Bradford's Law
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Bradford's law is a pattern first described by Samuel C. Bradford in 1934 that estimates the exponentially
diminishing returns In economics, diminishing returns means the decrease in marginal (incremental) output of a production process as the amount of a single factor of production is incrementally increased, holding all other factors of production equal ('' ceter ...
of searching for references in science journals. One formulation is that if journals in a field are sorted by number of articles into three groups, each with about one-third of all articles, then the number of journals in each group will be proportional to 1:n:n2. There are a number of related formulations of the principle. In many disciplines, this pattern is called a
Pareto distribution The Pareto distribution, named after the Italian civil engineer, economist, and sociologist Vilfredo Pareto, is a power-law probability distribution that is used in description of social, quality control, scientific, geophysical, actuarial scien ...
. As a practical example, suppose that a researcher has five core
scientific journal In academic publishing, a scientific journal is a periodical publication designed to further the progress of science by disseminating new research findings to the scientific community. These journals serve as a platform for researchers, schola ...
s for his or her subject. Suppose that in a month there are 12 articles of interest in those journals. Suppose further that in order to find another dozen articles of interest, the researcher would have to go to an additional 10 journals. Then that researcher's Bradford multiplier ''b''''m'' is 2 (i.e. 10/5). For each new dozen articles, that researcher will need to look in ''b''''m'' times as many journals. After looking in 5, 10, 20, 40, etc. journals, most researchers quickly realize that there is little point in looking further. Different researchers have different numbers of core journals, and different Bradford multipliers. But the pattern holds quite well across many subjects, and may well be a general pattern for human interactions in social systems. Like Zipf's law, to which it is related, we do not have a good explanation for why it works, but knowing that it does is very useful for librarians. What it means is that for each specialty, it is sufficient to identify the "core publications" for that field and only stock those; very rarely will researchers need to go outside that set. However, its impact has been far greater than that. Armed with this idea and inspired by
Vannevar Bush Vannevar Bush ( ; March 11, 1890 – June 28, 1974) was an American engineer, inventor and science administrator, who during World War II, World War II headed the U.S. Office of Scientific Research and Development (OSRD), through which almo ...
's famous article ''
As We May Think "As We May Think" is a 1945 essay by Vannevar Bush which has been described as visionary and influential, anticipating many aspects of information society. It was first published in ''The Atlantic'' in July 1945 and republished in an abridged v ...
'',
Eugene Garfield Eugene Eli Garfield (September 16, 1925 – February 26, 2017) was an American linguistics, linguist and businessman, one of the founders of bibliometrics and scientometrics. He helped to create ''Current Contents'', ''Science Citation Index'' ( ...
at the
Institute for Scientific Information The Institute for Scientific Information (ISI) was an academic publishing service, founded by Eugene Garfield in Philadelphia in 1956. ISI offered scientometric and bibliographic database services. Its specialty was citation indexing and analysis, ...
in the 1960s developed a comprehensive index of how scientific thinking propagates. His
Science Citation Index The Science Citation Index Expanded (SCIE) is a citation index owned by Clarivate and previously by Thomson Reuters. It was created by the Eugene Garfield at the Institute for Scientific Information, launched in 1964 as Science Citation Index ( ...
(SCI) had the effect of making it easy to identify exactly which scientists did science that had an impact, and which journals that science appeared in. It also caused the discovery, which some did not expect, that a few journals, such as ''
Nature Nature is an inherent character or constitution, particularly of the Ecosphere (planetary), ecosphere or the universe as a whole. In this general sense nature refers to the Scientific law, laws, elements and phenomenon, phenomena of the physic ...
'' and ''
Science Science is a systematic discipline that builds and organises knowledge in the form of testable hypotheses and predictions about the universe. Modern science is typically divided into twoor threemajor branches: the natural sciences, which stu ...
'', were core for all of hard science. The same pattern does not happen with the humanities or the social sciences. The result of this is pressure on scientists to publish in the best journals, and pressure on universities to ensure access to that core set of journals. On the other hand, the set of "core journals" may vary more or less strongly with the individual researchers, and even more strongly along schools-of-thought divides. There is also a danger of over-representing majority views if journals are selected in this fashion.


Scattering

Bradford's law is also known as Bradford's law of scattering or the Bradford distribution, as it describes how the articles on a particular subject are scattered throughout the mass of periodicals. Another more general term that has come into use since 2006 is information scattering, an often observed phenomenon related to information collections where there are a few sources that have many items of relevant information about a topic, while most sources have only a few. This law of distribution in bibliometrics can be applied to the
World Wide Web The World Wide Web (WWW or simply the Web) is an information system that enables Content (media), content sharing over the Internet through user-friendly ways meant to appeal to users beyond Information technology, IT specialists and hobbyis ...
as well. Hjørland and Nicolaisen identified three kinds of scattering: #Lexical scattering. The scattering of words in texts and in collections of texts. #Semantic scattering. The scattering of concepts in texts and in collections of texts. #Subject scattering. The scattering of items useful to a given task or problem. They found that the literature of Bradford's law (including Bradford's own papers) is unclear in relation to which kind of scattering is actually being measured.


Law's interpretations

The interpretation of Bradford's law in terms of a geometric progression was suggested by V. Yatsko, who introduced an additional constant and demonstrated that Bradford distribution can be applied to a variety of objects, not only to distribution of articles or citations across journals. V. Yatsko's interpretation (Y-interpretation) can be effectively used to compute threshold values in case it is necessary to distinguish subsets within a set of objects (successful/unsuccessful applicants, developed/underdeveloped regions, etc.).


Related laws and distributions

* Benford's law, originally used to explain apparently non-uniform sampling * Lotka's law, describes the frequency of publication by authors in any given field. *
Power law In statistics, a power law is a Function (mathematics), functional relationship between two quantities, where a Relative change and difference, relative change in one quantity results in a relative change in the other quantity proportional to the ...
, a general mathematical form for "heavy-tailed" distributions, with a polynomial density function. In this form, these laws may all be expressed and estimates derived. * Zeta distribution * Zipf's law, originally used for word frequencies * Zipf–Mandelbrot law


See also

*
PageRank PageRank (PR) is an algorithm used by Google Search to rank web pages in their search engine results. It is named after both the term "web page" and co-founder Larry Page. PageRank is a way of measuring the importance of website pages. Accordin ...
*
The Long Tail In statistics and business, a long tail of some distributions of numbers is the portion of the distribution having many occurrences far from the "head" or central part of the distribution. The distribution could involve popularities, random n ...


Notes


References

{{Scholia, topic * Bradford, Samuel C., ''Sources of Information on Specific Subjects'', ''Engineering: An Illustrated Weekly Journal'' (London), 137, 1934 (26 January), pp. 85–86. :Reprinted as: * Bradford, Samuel C. ''Sources of information on specific subjects'', Journal of Information Science, 10:4, 1985 (October), pp. 173–18

*Nicolaisen, Jeppe; and Hjørland, Birger (2007), ''Practical potentials of Bradford's law: A critical examination of the received view'', ''Journal of Documentation'', 63(3): 359–377. Availabl
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*Suresh K. Bhavnani, Concepcio´n S. Wilson, Information Scattering. Availabl

*Lancaster, F. W., & Pontigo J. (1986). Qualitative aspects of the Bradford distribution. ''Scientometrics'', 9(1–2), 59–70.


External links


In Oldenburg's Long Shadow: Librarians, Research Scientists, Publishers, and the Control of Scientific Publishing
Bibliometrics Computational linguistics Statistical laws