The rise and rise of citation analysis

been published in academic journals are never cited. Indeed, as many as 50% of papers are never read by anyone other than their authors, referees and journal editors. We know this thanks to citation analysis, a branch of information science in which researchers study the way articles in a scholarly field are accessed and referenced by others. Citation analysis is, however, about much more than producing shock statistics. Along with peer review, it has over the past three decades been increasingly used to judge and quantify the importance of scientists and scientific research. Citation analysis is also the machinery behind journal “impact factors” – figures of merit that researchers take note of when deciding which journal to submit their work to so that it is read as widely as possible. Indeed, the output from citation studies is often the only way that non-specialists in governments and funding bodies – or even those in different scientific disciplines – can judge the importance of a piece of scientific research. The Web has had a huge impact on citation-analysis research. Since the turn of the century, dozens of databases such as Scopus and Google Scholar have appeared, which allow the citation patterns of academic papers to be studied with unprecedented speed and ease. This could mark the beginning of the end for the 40-year monopoly of citation analysis held by the US-based firm Thomson Scientific, formerly known as the Institute for Scientific Information (ISI). The ISI’s citation databases have always been criticized by scientists on the basis that they index a limited number of journal titles, that they cover mainly English-language titles from North America and Western Europe, and that they do not cover citations from books and most conference proceedings. However, the myriad of Web-based sources now provides a much more comprehensive coverage of the world’s literature, helping to usher in a new era of citation analysis based on multiple sources. Furthermore, the Web has led to several new citation measures and methods that were previously impractical, including article-download counts, link analysis, Google’s PageRank, Web citations and the “h-index” recently developed by US physicist Jorge Hirsch.