Mainly, IF is a ratio intended for a given journal in a given year. This ratio is calculated by dividing the total number of citations received throughout the year for the publications in the given journal that were published in the two preceding years, by the totalchilloutshut harmonte-blaine donkeyluckycat 24bottlesclima benettonoutlet donkeyluckycat kleankanteenkinder senzamai harmonte-blaine lamilanesaborse fracominaoutlet scarpeovye kleankanteenkinder chilloutshut lecopavillon number of “citable items” or publications published in that journal during the two preceding years. It can be written as an equation as follows.
Impact factor (for a given year) = Total number of citations received within the given year for the publications that were published in the two preceding years/Total number of citable items published in two preceding years
For example, if a journal has an IF of 3 in 2008, then its papers published in 2006 and 2007 received three citations each on average in 2008. The 2008 IFs are actually published in 2009; they cannot be calculated until all of the 2008 publications have been processed by the indexing agency.
Therefore, IF denotes the yearly average number of citations of articles published in the last two years in a given journal. Impact factor can be calculated after completing the minimum of 3 years of publication. Because of this reason journal IF cannot be calculated for new journals. The journal with the highest IF is the one that published the most cited articles over a 2-year period. The IF applies only to journals, not to individual articles or individual scientists like the “H-index.”
IF is commonly used to evaluate the relative importance of a journal within its field. Journals with higher IFs are believed to be more important than those with lower ones. Hence impact factor can be used to compare different journals within a certain field.
Following are impact factors of some of the popular journals in the year 2019.
- Lancet 60.392
- Nature 42.778
- British Medical Journal 30.223
- JAMA-JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION 45.540
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