Journal Ratings: Methodology

The most commonly cited measure of a journal’s reach and impact is the ISI Web of Knowledge Impact Factor. There are several limitations to this metric. It relies upon a simple mean average of citations per article and is only available as a one- and five-year statistic. More importantly, not all journals are assessed, while citations in books and published conference papers are excluded.

Hirsch’s h-index eschews the skewed mean citations per article statistic, arriving instead at a number expressing the amount and magnitude of high-impact articles published by a journal during a given time interval. The index (h) for a journal is equal to the largest number h for which h articles were cited at least h times. An h-index of 10, for example, means that the journal published 10 articles that were cited at least 10 times, while an h-index of 50 means the journal published 50 articles that were cited at least 50 times.

The free software application, Publish or Perish, returns the h-index (and several other metrics) for any journal and any time interval. PoP searches use Google Scholar, which includes citations within books, conference presentations, and journals not measured by the ISI Impact Factor. A 2010 study by Jerry A. Jacobs argues convincingly that this method of assessing a journal’s impact is superior to the ISI Impact Factor.

The ratings on this site consist of the journal’s h-index for articles published between 2001 and 2010, as reported by PoP. The method is a replication of Jacobs’s study, albeit using a slightly different time interval. Citation searches were conducted in January 2011.

These ratings are not intended to be comprehensive or authoritative. They are likely to understate the impact of journals that publish fewer articles or issues and overstate the impact of journals with many articles or issues (e.g., ASR has a higher h-index than AJS, even though AJS articles on average are cited at a higher rate than ASR articles). They are also likely to understate the impact of new journals (e.g., Du Bois Review), since the articles with the most citations are more likely to have been published in the early 2000s. They provide a rough sketch–rather than an unimpeachable quantitative assessment–of which journals have published the most high-impact articles over the course of the past decade.

For a more detailed discussion of the quantification of journal impact (from which this description has drawn heavily), see Jacobs’s (2010) article.

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