- Email: [email protected]
Impact Factor
Editor’s Letter
Impact Factor
A
medical journal’s “academic worth” is to some degree measured by its impact factor. The words “impact factor” conjure up a variety of connotations, depending on preexisting impressions and publication or editorial experience. To some, impact factor serves as the only or, at a minimum, best measure of a medical journal’s prowess (“academic worth”). To others, it is but one of many means by which to measure such. To yet others, the value of the impact factor is nil—seemingly relegating it to the category of “metrics without meaning.” Finally, perhaps to the majority of consumers of medical information, impact factor is simply irrelevant. They consume the information they want to consume, regardless of journal impact factor. So, how does impact factor actually affect our assessment of a journal’s quality or “academic worth”? Let us begin with a definition. Impact factor is a metric that assesses the frequency that the “average article” in a journal has been cited in a given period of time. The impact factor for a given year is the average number of citations that year to articles published during the previous 2 years. For example, the impact factor for the year 2016 for a specific journal would be calculated as follows (from Journal Citation Report [JCR], a product of Thomson ISI [Institute for Scientific Information])1:
NUMERATOR: The number of citations in 2016 to articles published in 2014 and 2015. DENOMINATOR: The number of articles, or source items, published in 2014 and 2015. Impact Factor 2016 ¼ A/B Other lesser-known metrics for assessing journal performance are used, including the Journal Citation Report (JCR), a product of Thomson ISI (Institute for Scientific Information)1:
SJR ¼ SCImago Journal Rank: # times an average paper in a particular journal is cited . but assigns each citation a value >1.00 or <1.00 on the basis of the rank of the citing journal (uses 3-year window of measurement).
Each of these metrics is associated with both relative advantages and disadvantages. Regardless, for the discussion at hand here, we focus on Impact Factor. The Impact Factor of medical journals varies from <1 to >50 (e.g., New England Journal of Medicine). Most neurosurgery journals, including WORLD NEUROSURGERY, are in the 2e4 range. Why such a discrepancy? Well, quality most certainly plays a role. The magnitude of this discrepancy, however, is affected by other factors—the most important of which is what I call dimensional or mathematical in nature. Size of readership is a major issue. The New England Journal of Medicine reaches a huge readership and, hence, capitalizes on the much, much greater citation potential for each article than do neurosurgery journals. Neurosurgery journals cater to neurosurgeons only. Less than 1% of all physicians are neurosurgeons. Neurosurgeons and their journals are simply mathematically outnumbered here. Perhaps more importantly, though, is the potentially misleading nature of “ratings.” If Consumer Reports (a monthly magazine that rates commonly purchased products) rates a given product as the best in class by a large margin, all consumers should purchase the best in class product over all others—correct? Well, maybe, but we consumers are complex and assess many other factors when deciding on a purchase. We each harbor different and widely varying senses of aesthetics, perceptions of quality and value, and specific needs as they pertain to the product at hand. Hence, we may or may not choose to use Consumer Reports metrics in our decision making process. One thing is for certain—few of us use these reports as our sole decision making tool. Impact factor, in a way, is like a Consumer Reports rating. It has some value as an objective tool to assess journal quality and “academic worth.” However, this objectivity is associated with a relevance that is essentially indeterminate. Bottom line, the assessment of “academic worth” of a journal is and should be individualized. Everyone has discrepant senses of aesthetics and perceptions of quality and value, and we all have specific needs and desires as consumers of the medical literature.
SNIP ¼ Source Normalized Impact per Paper: measures contextual citation impact by weighting citations on the basis of the total number of citations in a subject field.
So believe what you must regarding impact factor and other related metrics. Just remember, you are the consumer. You have a choice regarding manuscript submission outlets and reading sources. Hence, impact factor should play whatever role you feel appropriate in your consumer-related decision making processes.
Article influence ¼ calculated by dividing the Eigenfactor score by the percentage of all articles recorded in the Journal Citation Reports that were published in a specific journal.
REFERENCE
The Eigenfactor score is a rating of the total importance of a specific journal. Journals are rated according to the number of incoming citations, with citations from highly ranked journals weighted to make a larger contribution to the Eigenfactor than those from poorly ranked journals. (Article influence and Eigenfactor exclude self-citations.)
WORLD NEUROSURGERY 102: XV, JUNE 2017
1. Reuters T. InCites Journal Citations Reports. Available at: https://jcr.incites. thomsonreuters.com/JCRJournalHomeAction.action. Accessed May 3, 2017. Ed Benzel To whom correspondence should be addressed: Ed Benzel, M.D. [E-mail: [email protected]] 1878-8750/$ - see front matter ª 2017 Published by Elsevier Inc. http://dx.doi.org/10.1016/j.wneu.2017.05.001
www.WORLDNEUROSURGERY.org
xv
Impact Factor
A
medical journal’s “academic worth” is to some degree measured by its impact factor. The words “impact factor” conjure up a variety of connotations, depending on preexisting impressions and publication or editorial experience. To some, impact factor serves as the only or, at a minimum, best measure of a medical journal’s prowess (“academic worth”). To others, it is but one of many means by which to measure such. To yet others, the value of the impact factor is nil—seemingly relegating it to the category of “metrics without meaning.” Finally, perhaps to the majority of consumers of medical information, impact factor is simply irrelevant. They consume the information they want to consume, regardless of journal impact factor. So, how does impact factor actually affect our assessment of a journal’s quality or “academic worth”? Let us begin with a definition. Impact factor is a metric that assesses the frequency that the “average article” in a journal has been cited in a given period of time. The impact factor for a given year is the average number of citations that year to articles published during the previous 2 years. For example, the impact factor for the year 2016 for a specific journal would be calculated as follows (from Journal Citation Report [JCR], a product of Thomson ISI [Institute for Scientific Information])1:
NUMERATOR: The number of citations in 2016 to articles published in 2014 and 2015. DENOMINATOR: The number of articles, or source items, published in 2014 and 2015. Impact Factor 2016 ¼ A/B Other lesser-known metrics for assessing journal performance are used, including the Journal Citation Report (JCR), a product of Thomson ISI (Institute for Scientific Information)1:
SJR ¼ SCImago Journal Rank: # times an average paper in a particular journal is cited . but assigns each citation a value >1.00 or <1.00 on the basis of the rank of the citing journal (uses 3-year window of measurement).
Each of these metrics is associated with both relative advantages and disadvantages. Regardless, for the discussion at hand here, we focus on Impact Factor. The Impact Factor of medical journals varies from <1 to >50 (e.g., New England Journal of Medicine). Most neurosurgery journals, including WORLD NEUROSURGERY, are in the 2e4 range. Why such a discrepancy? Well, quality most certainly plays a role. The magnitude of this discrepancy, however, is affected by other factors—the most important of which is what I call dimensional or mathematical in nature. Size of readership is a major issue. The New England Journal of Medicine reaches a huge readership and, hence, capitalizes on the much, much greater citation potential for each article than do neurosurgery journals. Neurosurgery journals cater to neurosurgeons only. Less than 1% of all physicians are neurosurgeons. Neurosurgeons and their journals are simply mathematically outnumbered here. Perhaps more importantly, though, is the potentially misleading nature of “ratings.” If Consumer Reports (a monthly magazine that rates commonly purchased products) rates a given product as the best in class by a large margin, all consumers should purchase the best in class product over all others—correct? Well, maybe, but we consumers are complex and assess many other factors when deciding on a purchase. We each harbor different and widely varying senses of aesthetics, perceptions of quality and value, and specific needs as they pertain to the product at hand. Hence, we may or may not choose to use Consumer Reports metrics in our decision making process. One thing is for certain—few of us use these reports as our sole decision making tool. Impact factor, in a way, is like a Consumer Reports rating. It has some value as an objective tool to assess journal quality and “academic worth.” However, this objectivity is associated with a relevance that is essentially indeterminate. Bottom line, the assessment of “academic worth” of a journal is and should be individualized. Everyone has discrepant senses of aesthetics and perceptions of quality and value, and we all have specific needs and desires as consumers of the medical literature.
SNIP ¼ Source Normalized Impact per Paper: measures contextual citation impact by weighting citations on the basis of the total number of citations in a subject field.
So believe what you must regarding impact factor and other related metrics. Just remember, you are the consumer. You have a choice regarding manuscript submission outlets and reading sources. Hence, impact factor should play whatever role you feel appropriate in your consumer-related decision making processes.
Article influence ¼ calculated by dividing the Eigenfactor score by the percentage of all articles recorded in the Journal Citation Reports that were published in a specific journal.
REFERENCE
The Eigenfactor score is a rating of the total importance of a specific journal. Journals are rated according to the number of incoming citations, with citations from highly ranked journals weighted to make a larger contribution to the Eigenfactor than those from poorly ranked journals. (Article influence and Eigenfactor exclude self-citations.)
WORLD NEUROSURGERY 102: XV, JUNE 2017
1. Reuters T. InCites Journal Citations Reports. Available at: https://jcr.incites. thomsonreuters.com/JCRJournalHomeAction.action. Accessed May 3, 2017. Ed Benzel To whom correspondence should be addressed: Ed Benzel, M.D. [E-mail: [email protected]] 1878-8750/$ - see front matter ª 2017 Published by Elsevier Inc. http://dx.doi.org/10.1016/j.wneu.2017.05.001
www.WORLDNEUROSURGERY.org
xv