Impact and other newer factors

Abstract

The impact factor (IF) has now been in use for some years, is well recognized by most readers, and may have some utility – but the disadvantages are also increasingly recognized. The five year Impact Factor, calculated in the same way as the regular IF, but measuring citations over a five year window rather than the two year window period of the regular IF, may reflect more accurately the impact of a journal. It has also been in use for some years. A new way of measuring journal influence is the Eigenfactor . Like the IF, the Eigenfactor score is essentially a ratio of number of citations to total number of articles. Eigenfactor is however, an estimate of the percentage of time that library users spend with a particular journal – which differs from the IF in that each citation is weighted according to the (importance) of the source. It weights each reference according to a stochastic measure of the amount of time researchers spend reading the journal. It excludes self citations but it counts citations to journals in both the sciences and social science. Each citation is given a value greater or lesser than 1 based on the Eigenfactor of the citing journal. A five year window of measurement is used (so the 2008 Eigenfactor examines citations received in 2008 from articles published 2003–2007). Thomson Reuters now include Eigenfactor metrics in Journal Citation Reports (JCR) but they are available only for years 2007 and later. Eigenfactor scores are scaled so that the sum of the Eigenfactor scores of all journals listed in JCR is 100. A journal Eigenfactor score is a measure of the journal’s total importance to the scientific