Thomson Reuters has recently updated the 2007 Journal
Citation Report to include 5-year Impact Factors for the first time.

Whereas the standard Impact Factor is the average number of citations in a given year, to articles published in the previous two years,  the 5-year Impact Factor presents a longer term view, showing the average number of citations in a given year to articles from the previous 5 years.

This provides a useful additional information about article impact that complements the standard Impact Factor, especially in fields where it may take several years for the true impact of research to become apparent.

Out of BioMed Central’s 42 journals with Impact Factors, 21 have been tracked for long enough to allow 5-year Impact Factors to be calculated by Thomson Reuters and these are shown below.

Many BioMed Central titles have improved rankings under this new metric. Perhaps the most striking example is Breast
Cancer Research, which is the 2nd highest ranked Breast Cancer journal in the standard Impact Factor rankings. Ranked onthe basis of its 5-year Impact Factor it overtakes the rival title Breast Cancer Research & Treatment, and is listed as the No. 1-ranked breast-cancer-specific journal by the 5-year metric.

A full listing of all BioMed Central journal 5-year Impact Factors, alongside the corresponding traditional Impact Factor, is given below: