Journal rankings and impact factors are quantitative measures for evaluating the performance of a journal in its field.
However, there are many different factors that influence the impact of a journal. Measuring impact it is not an exact science and should be used with an understanding of its limitations:
Quantitative measures of impact are often used in the Sciences, Medicine and Social Sciences but are not a useful measure of quality for Arts and Humanities journals.
Many journals only have their citations counted by Elsevier or Thomson Reuters. Neither tool is able to produce a complete count of citations. Journal rankings may, therefore, vary significantly between the two tools.
You should check all tools and carefully select the measurement you think best represents a journal.
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