Bradford's law is a pattern first described by Samuel C. Bradford in 1934 that estimates the exponentially diminishing returns of extending a library search. A quantity is said to be subject to exponential decay if it decreases at a rate proportional to its value. ... In economics, diminishing returns is the short form of diminishing marginal returns, the concept that, as more of an input is applied, each additional unit produces less and less additional output. ...

Here is how it works. Suppose that a researcher has 5 core scientific journals for their 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, you have to go to 10 journals. Then that researcher's Bradford multiplier b_m is 2 (ie 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, ... journals, most researchers quickly realize that there is little point in looking farther. A cover of the leading scientific journal Nature In academic publishing, a scientific journal is a periodical publication intended to further the progress of science, usually by reporting new research. ...

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 probably 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. This article may be too technical for most readers to understand. ...

However its impact has been far greater than that. Armed with this idea and inspired by Vannevar Bush's famous article As We May Think, Eugene Garfield at the Institute for Scientific Information in the 1960s undertook the development of a comprehensive index of how scientific thinking propagates. The creation of his 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 unexpected discovery that a few journals like Nature and Science were core for all of Hard science. The same pattern does not happen with the humanities or the social science - possibly because objective truth is so much harder to establish there. Vannevar Bush (March 11, 1890–June 30, 1974) was an American engineer, inventor, and politician, known for his political role in the development of the atomic bomb, and idea of the memex —seen as a pioneering concept for the world wide web. ... Vannevar Bushs essay As We May Think, first published in The Atlantic Monthly in July 1945, argued that as humans turned from war, scientific efforts should shift from increasing physical abilities to making all previous collected human knowledge more accessible. ... Following ideas inspired by Vannevar Bushs famous article As We May Think, Eugene Garfield at the Institute for Scientific Information in the 1960s undertook the development of a comprehensive index of how scientific thinking propagates. ... The Institute for Scientific Information (ISI) was founded by Eugene Garfield in 1960. ... Events and trends The 1960s was a turbulent decade of change around the world. ... A citation index keeps track of which articles in scientific journals cite which other articles. ... Nature is one of the oldest and most reputable general-purpose scientific journals, first published on November 4, 1869. ... Science is the journal of the American Association for the Advancement of Science. ... Hard science is a term which often is used to describe certain fields of the natural sciences, usually physics, chemistry, and many fields of biology. ...

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. With everyone armed with the same list, the definition of what journals were best became very important. And, of course, publishers had the same list, and therefore knew which journals they could charge more for. Which tightens pressure on universities, because when they have to spend more on the core journals, libraries have less latitude to buy other journals. And if they don't buy them, then papers in them do not get read, and therefore don't get cited, thereby making publication in them worth even less, tightening the spiral.

This price spiral has become known as the serial pricing crisis.

It has been argued that this problem with peer-reviewed paper journals is currently in the process of being replaced by electronic publishing. Electronic publishing can refer to the publication of ebooks and electronic articles, and the development of digital libraries. ...

See also

• PageRank

PageRank is a family of algorithms for assigning numerical weightings to hyperlinked documents (or web pages) indexed by a search engine. ...

External links

• In Oldenburg's Long Shadow: Librarians, Research Scientists, Publishers, and the Control of Scientific Publishing (http://www.arl.org/arl/proceedings/138/guedon.html)