Citation Data: The Wrong Impact? * * Reprinted with permission from Nature Neuroscience, 1, December, 1998, 641-643.

Every September a ripple of excitement passes through the scientific community as the Institute of Scientific Information (ISI) publishes its latest set of impact factors, in which some six thousand journals are ranked according to the number of citations they received in the previous year. The release of these results triggers elation or gloom in editorial offices around the world, but for many scientists it is no more than light entertainment, the scientific equivalent of tabloid gossip. For others, however, it represents something more serious, because their career prospects are increasingly affected by the impact factors of the journals in which they publish. Although bibliometric data undoubtedly have the potential to reveal significant insights into the quality of scientific work, they are also susceptible to abuse. It is therefore worth examining in some detail how they are derived and how they are now being applied. ISI is a commercial company based in Philadelphia, which publishes Science Citation Index and Current