|The impact factor of Drug Safety journal is a measure reflecting the average number of citations to recent articles published in the journal. It is frequently used as a proxy for the relative importance of a journal within its field, with journals with higher impact factors deemed to be more important than those with lower ones. The impact factor was devised by Eugene Garfield, the founder of the Institute for Scientific Information Drug Safety Impact factors are calculated yearly starting from 2013 for those journals that are indexed in the Journal Citation Reports. A journal can adopt editorial policies to increase its impact factor. For example, journals may publish a larger percentage of review articles which generally are cited more than research reports. Thus review articles can raise the impact factor of the journal and review journals will therefore often have the highest impact factors in their respective fields. Some journal editors set their submissions policy to "by invitation only" to invite exclusively senior scientists to publish "citable" papers to increase the journal impact factor. Journals may also attempt to limit the number of "citable items"âi.e., the denominator of the impact factor equation either by declining to publish articles that are unlikely to be cited or by altering articles in hopes that Thomson Scientific will not deem it a "citable item". As a result of negotiations over whether items are "citable", impact factor variations of more than 300% have been observed. Interestingly, items considered to be uncitable and thus are not incorporated in impact factor calculations can, if cited, still enter into the numerator part of the equation despite the ease with which such citations could be excluded. This effect is hard to evaluate, for the distinction between editorial comment and short original articles is not always obvious. For example, letters to the editor may refer to either class.