calculations from 1-, 5-, and 16-year periods and by use of
The Multiple Meanings of Impact Factors programs such as Access, or its equivalent, on any combination of years desired. We used the 1995 edition of this database to compute 7-and 15-year cumulative journal impact factors for Sir:
the 100 highest impact journals (Garfield, 1998). Many editors Harter and Nisonger (1997) raise some cogent semantic have claimed that current journal impact factors do not adeissues concerning journal impact factors. The term ''impact quately take into account the long half-lives of references cited factor'' was coined by me and Irving H. Sher in the early sixties in certain fields. Indeed, in this cross-disciplinary listing, one (Garfield & Sher, 1963). We first used the term as a simple can observe that journals in fields like physiology demonstrate means of comparing journals regardless of size. Anyone who a significant shift in rank. However, within the discipline itself, has used Journal Citation Reports is well aware that the jourthe changes in rank are less remarkable. Since most informed nal impact factor by itself does not tell the whole quantitative evaluators compare journals within disciplines, the work in story about a journal. That is why JCR has, from its inception, compiling long-term impact factors may prove to be primarily included data necessary to compute a variety of impact and of academic interest. Long-term impact can also be approxiproductivity measures. Productivity of articles (S), references mated by using current impact in combination with half-life (R), R/S (impact), and total citations for one or more years (Magri & Solari, 1996). Both actual citation frequencies or are among the data that can be used to characterize journals.
approximations provide a more realistic metric, rather than the Harter and Nisonger want to use the number of citations resimple ratio reflected in current impact factors. ceived in 1994 to articles published in 1992 and 1993. However, it is another variant on calculating productivity. It would not provide a journal user a standard of quality, independent of Eugene Garfield journal size. It is a mark of distinction for any new journal, Chairman Emeritus large or small, to achieve an impact comparable to the well-Institute for Scientific Information recognized leaders in its field.