Biomaterial Database

Evidence of methodologic bias in the derivation of the Science Citation Index impact factor. 1998

E J Gallagher, and D P Barnaby

Department of Emergency Medicine, Albert Einstein College of Medicine, Bronx, NY, USA.

OBJECTIVE The "impact factor" published in Science Citation Index (SCI) is widely used in the scientific community to measure the relative importance of a medical journal. In contrast to all other indicators of academic growth in emergency medicine, impact factors for emergency medicine journals have remained low and unchanged since the inception of the specialty. We wished to investigate this incongruity. METHODS We examined the methodology used to derive the SCI's journal impact factor. RESULTS The impact factor for journals is defined mathematically as the number of times a journal is cited over a period of time (the numerator) divided by the number of articles published by that journal during the same period (the denominator). Citation counts are derived from examination of all references contained in a subset of journals known as "source" journals. No emergency medicine journals are included in this group. The only source of citations for emergency medicine journals is from journals outside of emergency medicine. This produces small numerators with relatively constant denominators, leading to low impact factors. CONCLUSIONS The apparent failure of emergency medicine journals, as measured by the SCI impact factor, to keep pace with other indicators of academic development of the field is at least in part attributable to a methodologic bias inherent in the derivation of this factor.

UI	MeSH Term	Description	Entries
D010506	Periodicals as Topic	Works about publications issued at stated, more or less regular, intervals.	Journals as Topic,Magazines,Newsletters,Magazine,Newsletter
D012013	Reference Books	Books designed by the arrangement and treatment of their subject matter to be consulted for definite terms of information rather than to be read consecutively. Reference books include DICTIONARIES; ENCYCLOPEDIAS; ATLASES; etc. (From the ALA Glossary of Library and Information Science, 1983)	Book, Reference,Books, Reference,Reference Book
D004635	Emergency Medicine	The branch of medicine concerned with the evaluation and initial treatment of urgent and emergent medical problems, such as those caused by accidents, trauma, sudden illness, poisoning, or disasters. Emergency medical care can be provided at the hospital or at sites outside the medical facility.	Medicine, Emergency
D015706	Bibliometrics	The use of statistical methods in the analysis of a body of literature to reveal the historical development of subject fields and patterns of authorship, publication, and use. Formerly called statistical bibliography. (from The ALA Glossary of Library and Information Science, 1983)	Bibliography, Statistical,Analysis, Bibliometric,Bibliographies, Statistical,Bibliometric Analysis,Statistical Bibliographies,Statistical Bibliography,Analyses, Bibliometric,Bibliometric Analyses
D015982	Bias	Any deviation of results or inferences from the truth, or processes leading to such deviation. Bias can result from several sources: one-sided or systematic variations in measurement from the true value (systematic error); flaws in study design; deviation of inferences, interpretations, or analyses based on flawed data or data collection; etc. There is no sense of prejudice or subjectivity implied in the assessment of bias under these conditions.	Aggregation Bias,Bias, Aggregation,Bias, Ecological,Bias, Statistical,Bias, Systematic,Ecological Bias,Outcome Measurement Errors,Statistical Bias,Systematic Bias,Bias, Epidemiologic,Biases,Biases, Ecological,Biases, Statistical,Ecological Biases,Ecological Fallacies,Ecological Fallacy,Epidemiologic Biases,Experimental Bias,Fallacies, Ecological,Fallacy, Ecological,Scientific Bias,Statistical Biases,Truncation Bias,Truncation Biases,Bias, Experimental,Bias, Scientific,Bias, Truncation,Biase, Epidemiologic,Biases, Epidemiologic,Biases, Truncation,Epidemiologic Biase,Error, Outcome Measurement,Errors, Outcome Measurement,Outcome Measurement Error