Hjã ̧rland B, & Nicolaisen J, Bradford`s Law of Dispersion: Ambiguities in the Concept of the “Subject”. Crestani F, & Ruthven I: Information Context: Nature, Impact, and Role Berlin, Springer, 2005. 96â106 The authors are currently studying various issues related to Bradford`s law of dispersion. The project is partly funded by the Danish Ministry of Culture [A2004 06-026]. In an article entitled “Sources of Information on Specific Subjects” (Engineering 137 , 85-6), Samuel C. Bradford, a British mathematician, librarian and documentary filmmaker at the Science Museum in London, published Bradford`s Law, also known as “Bradford`s Law of Dispersion” and “Bradford Distribution”, which shows the “exponentially diminishing returns of expanding a library search”. Bradford`s law of dispersion is supposed to be the dispersion of subjects in sources of information. Despite a body of writing on the meaning of the word “subject” and equivalent terms such as “about” or “actuality”, the meaning of “subject” has never been explicitly addressed in relation to Bradford`s law. This article introduces a distinction between lexical diffusion, semantic diffusion, and subject diffusion. Neither Bradford himself nor any follower explicitly took into account the differences between these three and the implications for the practical application of Bradford`s law. Traditionally, Bradford`s law has been seen as a neutral and objective tool for selecting the most central sources of information in a region. However, it is difficult to find actual reports describing how Bradford`s Law has been applied in practical libraries and information services.
Theoretical and historical evidence suggests that the selection of journals based on Bradford distributions tends to favor dominant theories and viewpoints, while suppressing views other than the mainstream at some point. Rao, I.K.R.: An analysis of Bradford multipliers and a model for explaining the law of diffusion. Scientometrics 41(1/2), 93–100 (1998) Bradford`s law of dispersion is a law of diminishing yield and dispersion. Bradford formulated the law in 1948, stating that for a particular field there are “very productive magazines, a greater number of more moderate producers, and an even greater number of ever-decreasing productivity” . For each issue or individual domain, the upper third (Zone 1 or Core) represents the journals most frequently cited in the literature on the subject and which are therefore of the greatest interest to researchers in the discipline. The middle third (zone 2) includes journals that had an average number of citations, and the bottom third (zone 3 or tail) includes the long tail of journals that are rarely cited and considered marginally important to the subject . Researchers have defined a topic in lexical, semantic, and subject diffusion terms , and some argue that problems may not play a role in defining the “topic,” provided it is applied consistently . Hjørland and Nicolaisen (2005, p.
1). 103) identified three types of dissemination: Bradford`s law of dispersion defines an exponential decreasing return on expanding a reference search in journals and can be used to identify “core journals” in a field. The aim of this study was to identify basic reviews of paediatric surgery. There are many mathematical approaches that apply Bradford`s distribution law to datasets.4,5,18,26 This study uses the Egghe extension of the Leimkuhler method used in other studies.5,18,19,26 This formulation relies on the use of exponential functions to predict zonal distribution and depends on the parameters of the citation database of the total number of citations by the best journal and the total number of journals; However, no mathematical formulation has achieved consistent statistical significance.9 Furthermore, how does this type of analysis compare to the more traditional ranking of journals that the IF uses? The journal IF is defined as the average number of citations per article in the last 2 years of publication. This value is relevant for journals to compare their impact with that of other journals in equivalent fields of study. Due to the magnitude of the differences in readership, it does not make sense to compare journals across disciplines. For example, the Journal of Neurosurgery and the New England Journal of Medicine have both been found as basic journals for neurosurgery, but their IFs are very different (3,227 vs. 54.42 and [2013 IF], respectively).
The value of a Bradford legal analysis is that it attempts to analyze the usefulness of a particular topic or field, regardless of the relative overall impact, and includes journals beyond the traditional barriers of the field. They found that the literature of Bradford`s law (including Bradford`s own articles) is unclear in terms of the type of dispersion actually measured. With the approval of the Institutional Review Board, we have developed bibliometric profiles for the best academically productive pediatric surgeons in the United States. These profiles included the total number of publications, the journals in which these authors published their manuscripts, and the identification of all articles cited by these surgeons, as well as the journals from which these references originated. Bradford`s law of dispersion was applied to identify basic reviews of pediatric surgery. Basic journals have been identified in many areas using Bradford`s law of dispersion, including environmental and occupational medicine,23 nursing,24 physiotherapy and rehabilitation medicine,7 physiotherapy,6 physics,26 and science.4 In 2013, Madhugiri et al.19 were the first to apply the Bradford Dissemination Act to identify basic journals in the field of neurosurgery. They looked at all review references from the top 11 neurosurgical journals based on impact factor (IF) over a 3-month period, with the exception of special and targeted issues where many articles on a particular topic were published. They were able to classify Bradford`s law into 3 zones (p) for a total of 182 journals, with the 6 main journals in Zone 1 being Journal of Neurosurgery, Neurosurgery, Spine, Acta Neurochirurgica, Stroke and Journal of Neurotrauma.19 In addition, in 2014 we applied Bradford`s law to the field of pediatric neurosurgery.15 We reviewed all articles published over a 5-year period from the top 25 North American pediatric pediatricians. Neurosurgeons based on the h-index, as well as the 25 best European pediatric neurosurgeons.