Source: ISI Web of Science


Back to Home Page

In the beginning, during the late 1950s, it was just an innocent idea in Eugene Garfield's head. A Philadelphia researcher who described himself as a "documentation consultant," Mr. Garfield spent his free time thinking about scientific literature and how to mine information from it. He eventually dreamed up something he called an "impact factor," essentially a grading system for journals, that could help him pick out the most important publications from the ranks of lesser titles. .......from Chronicle of Higher Education, October 14, 2005

The increased publicity of ISI  Impact Factor of scientific journals has led  to  some misgivings.  
Please refer to the  article published in Nature, "Not-so-deep impact: Research assessment rests too heavily on the inflated status of the impact factor" Nature Vol. 435, 1003 (23 June 2005).  ".....For example, we have analysed the citations of individual Nature and found that 89% of last years figure was generated by just 25% of our papers. ....." 

Read the article from Chronicle of Higher Education, "The Number That's Devouring Science" -The impact factor, once a simple way to rank scientific journals, has become an unyielding yardstick for hiring, tenure, and grants.   Read Chronicle of Higher Education, October 14, 2005

Similar viws have also been expressed in another article relatated to education and debate Why the impact factor of journals should not be used for evaluating research (BMJ 1997;314:497, 15 February)

The Impact Factor of the scientific journals are determined from the short term citations (two previous years) and does not consider long term impact.   Increase/decrease in number of published papers in a given year, time required to publish articles, and publication of popular review articles indirectly influence the Impact Factor.  

In order to assess the real  impact of published work, a Citation Frequency for published work has been determined for selected journals during 3 different periods: 1. Short term (2002-2004); 2. Medium term (1998-2004) and  3. Long term (1975-2004). The fraction of the published papers that show significant citations (25, 50 or 100+ citations); moderate citations (10+ citations) and No citations are compared for these three differemt periods. 
For further details on the analysis of Citation Frequency please refer to

Citation Frequency of Published Papers during 2002-04; 1998-2004  and 1975-2004

Citation Frequency = Number of Papers with N citations/Total Number of Published Papers x100

Where N represents number of papers with at least 100, 50, 25, 10 or no citations.

Here is a comparision of 30 most cited papers that were published in few selected journals during  three different periods.  The impact factor of these journals in the Physical Chemistry/Chemical Physics area vary from 2 - 9.  It is interesting to note that all these journals have published many papers with impressive citations.  If the scientific work is novel and significant, it is sure to make an impact irrespective of the journal impact factor.

(All data presented here was gathered from ISI Web of Science on August 27, 2005)

Impact FactorImpact Factor Phys Chem