Impact Factor

The impact factor (IF) or Journal impact factor (JIF) of an academic journal is a measure reflecting the yearly average number of citations to recent articles published in that journal. It is frequently used as a proxy for the relative importance of a journal within its field; journals with higher impact factors are often 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. Impact factors are calculated yearly starting from 1975 for those journals that are listed in the Journal Citation Reports.

In any given year, the impact factor of a journal is the number of citations received in that year by articles published in that journal during the two preceding years, divided by the total number of articles published in that journal during the two preceding years:

${\displaystyle {\text{IF}}_{y}={{\text{Citations}}_{y-1}+{\text{Citations}}_{y-2} \over {\text{Publications}}_{y-1}+{\text{Publications}}_{y-2}}}$

...
Wikipedia