Traditionally, journal quality has been assessed through the ISI Journal Impact Factor (JIF). This chapter proposes an alternative metric Hirsch's h-index and data source Google Scholar to assess journal impact. Using a comparison between the Google Scholar h-index and the ISI JIF for a sample of 838 journals in Economics & Business, I argue that the former provides a more accurate and comprehensive measure of journal impact.
The h-index has several important advantages over the Thomson ISI JIF. First of all, it does not have an artificially fixed time horizon. The metrics used in the present chapter were computed in October 2007 over a five-year period (2001-2005) in order to enable a comparison with the average JIF for 2003-2007 (for further details see the section on procedures). However, any time horizon could be used, rather than focusing on citations in one particular year to the two preceding years as is the case with the Thomson ISI JIF.
Second, the h-index attenuates the impact of one highly-cited article, because unlike citations-per-paper measures such as the JIF the h-index is not based on mean scores. In a citations-per-paper metric even one highly-cited article can cause a very strong increase in the average number of citations per paper for the journal in question, leading to possibly highly idiosyncratic and variable results. When we choose to evaluate journal impact through citation impact measures, we are interested in the overall citation impact of the journal, not in the citation impact of one or two highly cited individual papers in that journal.
Third, the h-index is influenced by the number of papers that a journal publishes. A journal that publishes a larger number of papers has a higher likelihood though by no means certainty of generating a higher h-index since every article presents another chance for citations. This may be seen as a disadvantage when evaluating the standing of individual articles in a journal (or an individual academic based on this metric) as this measure should not be dependent on the number of articles published in that journal. However, one cannot deny that a journal that publishes a larger number of high-impact papers has a bigger impact on the field. Given that impact on the field is what we attempt to measure, this feature of the h-index and g-index is an advantage rather than a disadvantage.