Select Committee on Science and Technology Written Evidence


Annex 1

EXPLANATION OF IMPACT FACTORS AS A MEASURE OF QUALITY

  The Institute of Scientific Information (ISI), a commercial company based in Philadelphia, collates information on citations of articles in several thousand of the world's major science journals. Each year, they produce a Science Citation Index. This lists each journal covered and ranks it according to average numbers of citations to its articles. In year x, it takes account only of articles cited during year x and published during years x-1 and x-2. Thus, it assesses only articles published and cited during a specific window of time. An article that is so ground-breaking that it is cited in its year of publication will not be included (although it is likely to continue to feature well during the relevant two years). Equally, an article whose worth is only recognised later, or which continues to be cited for many years, will not necessarily have full influence on the impact factor.



 
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