The impact factor of the Netherlands Heart Journal in 2013

Excerpt

Impact factors of scientific journals divide the number of received citations during a (citation) year by the number of papers published in the past; normally the 2 years preceding the year of the citation count. These impact factors have -widely and for almost 20 years- been criticised when it comes to a translation of the impact factor of a journal to its constituent papers [1‐4]. The reason is that the distribution of citations over the papers of a journal is heavily skewed [2, 4]. Therefore, there is a large difference between the average number of citations (impact factor) and the median number of citations. The explanation for this discrepancy is incomplete but relates to, among other things, the number of scientists active in the same field. Efforts have been made to relate obtained citations to the source of citations, i.e. the citing authors, their field, including their citation behaviour [5‐8], but there is inhomogeneity in citation density below the level of a scientific journal [9] and thus far no satisfactory solutions for this problem have been found. Relating citations to medical subject headings (MeSH) of bibliometric retrieval systems may be a step forward [10], but this would still depend on categorisation of science by others than the publishing authors. True as this may be, it does not mean that impact factors are not important for scientific journals, their owners, their publishers, their editors, their reviewers and their prospective authors. The importance is also substantial for those who are in charge of judging applications for research grants and academic positions. …