Librarians and information scientists have been evaluating journals
for at least 75 years. Gross and Gross conducted a classic study of
citation patterns in the '20s.
Others, including Estelle Brodman with her studies in the '40s of
physiology journals and subsequent reviews of the process, followed this
lead.
However, the advent of the Thomson Reuters citation indexes made it
possible to do computer-compiled statistical reports not only on the
output of journals but also in terms of citation frequency. And in the
'60s we invented the journal "impact factor." After using journal
statistical data in-house to compile the Science Citation Index® (SCI®) for many years, Thomson Reuters began to publish Journal Citation Reports® (JCR®) in 1975 as part of the SCI and the Social Sciences Citation Index® (SSCI®).
Informed and careful use of these impact data is essential. Users may
be tempted to jump to ill-formed conclusions based on impact factor
statistics unless several caveats are considered.
