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ABSTRACT
THIS ESSAY PROVIDES AN OVERVIEW of journal evaluation indicators. It highlights the strengths and weaknesses of different indicators, together with their range of applicability. The definition of a "quality journal," different notions of impact factors, the meaning of ranking journals, and possible biases in citation databases are also discussed. Attention is given to using the journal impact in evaluation studies.
The quality of a journal is a multifaceted notion.Journals can be evaluated for different purposes, and hence the results of such evaluation exercises can be quite different depending on the indicator(s) used. The impact factor, in one of its versions, is probably the most used indicator when it comes to gauging the visibility of a journal on the research front. Generalized impact factors, over periods longer than the traditional two years, are better indicators for the long-term value of a journal. As with all evaluation studies, care must be exercised when considering journal impact factors as a quality indicator. It seems best to use a whole battery of indicators (including several impact factors) and to change this group of indicators depending on the purpose of the evaluation study. Nowadays it goes without saying that special attention is paid to a journals and specific indicators for this type of journal.
INTRODUCTION
Few model-based approaches to journal evaluation can be found in the literature. A descriptive, but not explanatory model is the one used by the Leiden-based Centre for Science and Technology Studies (Tijssen & van Raan, 1990). Perhaps this overview will inspire fellow scientists to construct an overall model explaining observed journal citation scores, and hence lead to a better understanding of their role in institutional and national evaluations. Theoretical issues dealt with in this article are restricted to giving precise formulations of indicators, in particular of the journal impact factor. No input-output model or explanation of dependent variables, such as journal citation counts, as a function of one or more independent variables (e.g., number of journals in the field or number of active scientists) is provided.
The study of the use and relative impact of scientific journals is an important application of citation analysis. Yet citations are only one aspect of a journal evaluation exercise. Indeed, journal evaluation can be performed with...