What are impact factors? How do I locate them? How do I use them?
Definition: Impact factors. The name seems explanatory, but the entire concept and definition remains mysterious and vague to a lot of researchers. Essentially, the impact factor represents a metric that measures the relative influence and significance of a journal within its particular discipline.
How they are calculated: Impact factors are calculated through a very specific formula: Cites to recent items (previous two years of a journal's publications) divided by the Number of recent items (past two years)
Where they are located: Not all journals receive impact factors, since only journals indexed in Journal Citation Reports receive an impact factor. Journal Citation Reports is published by Thomson Reuters, which also owns and publishes ISI Web of Science, where you can also connect to information about a journal and its impact factor.
I've created two short (each about a minute), silent screencasts to show you each of these two methods. To enlarge the screencast, click on the little square icon with the circle in the middle. If you're reading this in any sort of blog reader, you'll need to click through to see the screencasts.
Using JCR to locate impact factors
Using Web of Science to locate impact factors
How and why to use them: Impact factors are used to determine the most influential journals in a particular field. You may want to locate these journals for a number of reasons: 1) to find research from the most authoritative journals and 2) to submit your research for publication to the most influential/widely read journals.
Many researchers also use the impact factor as a metric for promotion and tenure assessment. Although impact factors may not be a good sole indicator of a researcher's impact (see criticisms below), this metric can still provide helpful information during the tenure and review process.
Criticisms: Many researchers feel that the impact factor is an inadequate or inappropriate method for assessing a journal's significance or impact. Criticism of the impact factor usually revolves around several different reasons: 1) that IF represents an arithmetic mean, rather than a normal distribution; 2) that different disciplines may have different representation in JCR, or exhibit different readership and research patterns, which could affect the rate of citations; 3) that journals can manipulate their editorial policies to include more review articles (more highly cited) or fewer citable items (a better ratio); 4) that impact factor still includes an author's self-cites.
Regardless of the criticisms, impact factor remains the most widely used assessment metric for journals. Other, alternative assessment metrics include: H-Index (more author based), Eigenfactor, or the Google Scholar Citation Counter.
Further reading:
Many researchers also use the impact factor as a metric for promotion and tenure assessment. Although impact factors may not be a good sole indicator of a researcher's impact (see criticisms below), this metric can still provide helpful information during the tenure and review process.
Criticisms: Many researchers feel that the impact factor is an inadequate or inappropriate method for assessing a journal's significance or impact. Criticism of the impact factor usually revolves around several different reasons: 1) that IF represents an arithmetic mean, rather than a normal distribution; 2) that different disciplines may have different representation in JCR, or exhibit different readership and research patterns, which could affect the rate of citations; 3) that journals can manipulate their editorial policies to include more review articles (more highly cited) or fewer citable items (a better ratio); 4) that impact factor still includes an author's self-cites.
Regardless of the criticisms, impact factor remains the most widely used assessment metric for journals. Other, alternative assessment metrics include: H-Index (more author based), Eigenfactor, or the Google Scholar Citation Counter.
Further reading:
- Thomson (ISI) products useful in promotion and tenure, from Virginia Tech Libraries
- The Thomson Reuters Impact Factor, from Thomson Reuters
- The Agony and the Ecstasy—The History and Meaning of the Journal Impact Factor, by Eugene Garfield
- The Number that’s Devouring Science, from The Chronicle of Higher Education
No comments:
Post a Comment